I'm getting increasingly confused. What 'earth terminal' are you talking about?
The earth "pin" on the PSU - which has an oddball crackpot connector dreamt up by Apple - because clearly, for Apple, there aren't enough standards they don't already own.
Clearest image I could find quickly is
on this page - though I don't recommend the alternative use !
It varies - some PSUs have a plastic stud, some have a metal one. There are two types of adapter to actually connect these to the mains : Some are what are often called "duckhead" (because with the US version fitted to certain PSUs, it can look a bit like a ducks head) - and at least for the UK version doesn't have an earth contact. They also do cables which for the UK and European versions do have an earth contact.
[I take it that you mean 0.035mA]... which, if such were what it was due to, would correspond to a capacitance of ~1000 pF - which I assume is way out of the ballpark of any 'stray capacitance'.
As a matter of interest, what multimeter have you got that can measure AC microamps?
It's an older version of
this YF-3503 which I was surprised to find as what looks like a current product. The version I have is third down
here.
As you can guess, finest Taiwanese engineering - but it's done me good service for many years, I think I must have had it for at least 25 years ! My biggest gripe is that the sockets don't take fully shrouded plugs. They have a recess, but it's not the full depth. And IIRC, the tracks on the PCB for the 20A connection were "a bit on the light side" but I was able to fit the smoke back in and fix it.
And as I looked up those images, I had a bit of an idea. While the meter has capacitance measurement, I've never actually used it. I twigged that the fine test prods I have would fit the socket, and I have test clips to fi the other end. So a quick measurement later, and I can tell you that in my supply, there is something in the order of 250pF between each mains pin of the supply and the earth stud.