Well I figured it out myself moments after posting the question. Turns out it was a silly mistake, but I'll put it here anyways before closing the question so as to help any future minecrafter who may stumble on the same problem.

I had the target and amount backwards. Instead of "/xp @a[-1,230,-11,5,m=0,lm=1] -1L", it needed to be "/xp -1L @a[-1,230,-11,5,m=0,lm=1]".

Ive learned from my mistake. maybe my experience can be of use to another.

Well I figured it out myself moments after posting the question. Turns out it was a silly mistake, but I'll put it here anyways before closing the question so as to help any future minecrafter who may stumble on the same problem.

I had the target and amount backwards. Instead of:

/xp @a[-1,230,-11,5,m=0,lm=1] -1L

It needed to be:

/xp -1L @a[-1,230,-11,5,m=0,lm=1]

I've learned from my mistake. Maybe my experience can be of use to another.