My sincere apologies; this is my first year filing 8960 (I'm not really sure why it never triggered in the past). I figured out my error: I wasn't accounting for my investment gains/losses (2023 line 5a). Since I had a capital gain loss on 1099-B, it subtracts from INT and DIV, and gets me to the exact calculation TurboTax reports.
Thanks for the help! Sorry I co-opted the post (this probably deserved it's own topic)!
