According to the EFL, you can have 25 players registered to play. If a player is U21 at the start of a season, they don't have to be registered UNLESS they're a loan player, in which case they do even if they're under the age of 21. Being under 21 classes anybody who was born after January 1st 2004, which as it stands is nobody that isn't on loan. We need eight home grown players (spent three years at any English or Welsh club before they turned 21). We also need one club developed player in the registration rules, which is a player that's spent at least one year in our U18s, which presumably is why they've hung onto Matty Jacob (guessing they planned for Cartwright to go out on loan as he's 22 and would need to be registered, but then got injured and we signed Rushworth anyway). Vaughan and TSF joined in the U21s I believe, so they wouldn't count.
So we basically need to deregister the injured/banned players to free up three spaces, shipping out Longman, Bedia, Mehlem, Rushworth and Burns during this window would then give us eight free spaces, which tracks with the amount of signings Acun said we'd make. If Vaughan went out, that would also free up a space. I have no idea what's happening with Sinik; he has a one year option on his contract and presumably Selles wants to see if he can be of any use before making a decision as even if we're letting him go for free in the Summer, if he can contribute it's one less winger to have to worry about.
I've just checked the list submitted to the EFL, because I forgot about Jarvis and Smith. They were both registered in the first team squad (unless Baz has ****ed this up, surely not), while Vaughan and Kamara were listed as U21s. I'm not sure what's going on because Kamara was born on July 21st 2003, Simons is older being born on February 20th, unless they're counting the start of the following season as where they start counting from, that's the only reason I can think it would count.