I love being a nerd

Genie in the OP image would've said "OK you now have 0 wishes".

Since he said 255, my interpretation is a valid solution.

Of course, if we're talking hypothetical wish gaining prevention methods, I'd just have a check before,

previous_wishes = wishes;

{Do all the wish things. wishes ends up with a 255 because of our shenanigans}

If(wishes>=previous_wishes) wishes = previous_wishes-1;

;If the current number of wishes isnt less than the old number of wishes, set it to the old number and subtract 1

If(wishes==0) {/*TODO: write function to end wish giving sequence*/}

You have 3 wishes.

First wish: I wish my last wish would count as me consuming two wishes. Second wish: I wish to have 0 wishes remaining.

First wish puts you down one wish, so ending at 2. Second wish removes one wish, so at one, then wish happens putting you at 0,

then because this second wish now becomes your last, as you have 0 remaining, the first wish then takes effect and consumes another wish, putting you to - 1 and overflowing.

Didn't even get the joke here because this is how I always imagined genie wishes working.

I would assume this to be the case since you cannot un-utter a wish—once you say it, it is counted as a wish before it's fulfilled.

If the counter is decremented only after the wish is fulfilled, then this means you can go back on wishes because they don't count until they're fulfilled, which goes against the lore.