Deleting daily backups

I’ve been doing a daily backup to the local disk for quite some (then that disk is backed up) and the backup files are accumulating. I noticed that there is a “delete after…” setting. If I do and change this to something like 10 days will the system delete all those old files or will I have to catch it up manually?

I use delete after … runs

for example; delete after 7 runs;
it will erase the first backup when it completes 8th run.

if you use days, take backup or not it will erase automaticly after that day