From your screenshot you have many incrementals which the expiration period is far out in the futures. This means in your job setup the incremental state retention period is large or could be larger than the full stage retention period.
You should be able to click at the bottom to delete the dependent sets - this of course would delete the the entire set and all those incrementals.
Thanks for the reply.
I set it to 12 weeks retention originally but now i changed it to 8 weeks in the last week or so.
I've just tried to remove 1 of the oldest ones and it mentioned about the dependanies, so i said delete and dependenies and i've had the following error. See attached.