Parasitic drain.

My 2004 Ford Courier ute loses charge in the battery if the car sits for four days or more. Before I retired I wouldnt notice it because I was using it every day and it got charged up.
The battery is brand new and shows 12.7V
I performed a parasitic draw test by following a youtube video. It only registers a reading with the multimeter on the 10A setting and plug. It shows .01 Is this acceptable? I'm thinking it is because If I change to lower settings on the multimeter I get no reading at all.
If the alternator had a faulty diode causing a discharge, would it show up on the test I have done?

Do you leave the key in it ?

the ignition switches in the Ford courier ,can become worn out and dirty inside the contacts , if you have trouble with the key starting the vehicle it may be the switch ,it can cause a drain across terminals inside the unit ,easily replaces but a bit expensive, around $125 for mine

To eliminate alt as the drain . try the simple ol school "touch" test with the key out ,all doors shut incl glove box lid ,radio off ,leaving multimeter aside ,remove + cable from the batt terminal and just touch connect ,there should be no spark at all and if there is and If you suspect the alternator remove/disconnect the charge wire at the battery .then re-test ,there should be no spark on the touch test at all.If there is slight spark while charge wire is connected,need to look further at alt. or barrel sw.unplug barrel or other items like even the clock if it has one . until you find it.

Boot or glovebox, or even interior light?
Disconnect that fuse & try the 'touch test ' with the battery leads.

The last car I bought had a broken glovebox hinge, which left the switch on, and a fallen roof lining was covering a rear interior light that had been left on.
I swapped as many interior & door lights over to LED as possible, it was a great improvement & uses less power.

Also, charge the battery up properly with a good battery charger, I have found a couple of times that this fixed the problem. ( And that one of 2 identical chargers I have, just won't charge the battery properly )

For some reason, which never made sense to me, my computer tablet would flatten even a brand new car battery.

.01 amp is 10ma anything under 30ma is fine. When is the 12.7v measured. Straight after use or when its been sitting. Is your amp meter working. Quick way to test amp meter when connected is see if current increases when you turn on interior light. Have you had the battery tested?

Is it a calcium battery?
Wondering if its not getting enough voltage to charge it properly, and it is only getting a surface charge. Have you checked voltage with it running/charging?
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quotes-
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However, once a calcium battery goes flat it needs a seven stage bench charge to bring it to 100% state of charge (SOC)

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Calcium batteries are the most commonly fitted battery; they also go by the name of ‘wet lead acid’ batteries. The basic ingredients are no different to the old style, but these batteries are more durable and have more starting power. They have a good shelf life and are maintenance free. But they require regular use, so when drained they must be recharged using a charger to bring them back to optimal health. Modern vehicle charging systems will struggle to recharge these fully when they’re drained.
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I had one i took back to supplier, wanting it replaced under warranty, as it was doing the same(flat if unused for 3 days), and my standard chargers did not recover it(and yes i had let it get dead flat due to little use of that vehicle over winter).
They put it on a higher voltage charger for 24 hours, and gave it back, and it was fine still when i sold vehicle a year later.

The new battery is a calcium battery which seems to be taking a charge just fine. I installed it and it went fine, then left the vehicle for four days and it only just started. After driving it there were no problems starting, and I havent left it sitting more than overnight which results in good starting in the morning.
I thought the measured drain was minimal, I'll just keep monitoring it.
The Ammeter works fine, and registers even a small increase in current like turning on the interior light.

Perhaps worth leaving battery "Disconnected" for it's usual 4 days sitting unused, and check it's voltage is still 12.7, so as to prove its not the batteries fault. (wondering if it has an internal short?)

Perhaps worth leaving battery "Disconnected" for it's usual 4 days sitting unused, and check it's voltage is still 12.7 and starts vehicle easily still, so as to prove its not the batteries fault. (wondering if it has an internal short?)