Sounds like it's amortization. IRL, transfer fees are (obviously) paid in full when a transfer occurs. However, for accounting purposes that money is spread evenly over the length of the player's contract. Sign a $10 million player for 5 years, and the fee will hit your books at $2 million annually, or roughly $167,000 monthly. So what you're seeing is the amortized cost of all transfer fees on your books, including those made before you even assumed the helm. It doesn't matter what you did or didn't actually spend in a given month. (This is for incoming players only. Payments received for outgoing players immediately hit your books in full.) That's how it works in actual life, anyway. Sounds like that's how it works in FM, too. I've never actually checked, lol.
Yeah...I should have checked my own save before replying. Zero transfer spend this month.