Sounds like typical military finance SNAFU. Army finance is notorious for screwing up military pay. And believe me, it takes forever to fix a pay problem. BTW, most stateside finance offices have a majority of civilian workers, which is part of the problem, due to the fact that GS employees are seldom held accountable for their mistakes.
"...it takes forever to fix a pay problem"
Ha, sort of. If you were overpaid, the Army can fix that awfully fast. Expect to eat nothing but chow hall food for a bit.
If you were underpaid for a period, and the Army therefore owes you $$, you can expect 10% of the balance paid over the next 2 pay periods, followed by quarterly installments for the next 3-7 years until the amount is paid (however small that amount is), or some other similarly ridiculous arrangement.