^^ and do you have printouts showing the past payment history, or anything like that, which will help you to prove on paper that this payment was short? I believe you, 100%; I want you to be able to go in to the supervisor (or whoever) with hard evidence so the odds are better that you'll come out with your missing money
because sadly the first response of many people is to bristle, deny, and defend - a calm demeanor and documented proof can defuse that - sometimes, anyway.
Not sure if this is a contractor/freelancer payment, a stipend like SSDI, or ?? but hopefully there's historical documentation like a benefits letter or bank statements.
Best to you. And a warm pat on the shoulder, or your preferred equivalent.
_________________
"I believe you find life such a problem because you think there are the good people and the bad people," said the man. "You're wrong, of course. There are, always and only, the bad people, but some of them are on opposite sides."
-- Terry Pratchett, Guards! Guards!