Control size of backup

I’ve been using Comodo Backup on a Windows 7 machine for a few months. I do a daily differential backup and a full backup monthly - everything to an external hard drive. The external HD (2TB) is now full. I’m thinking there should be some obvious way to control the maximum size of the backups so that the program automatically manages the disk space, but I can’t seem to find anything.

Any suggestions?

Thanks.

Yes, erase your older backups.

I feel really stupid asking this question, but I can’t figure out how to erase older backups. The file on my external HD is just one gigantic file and I don’t see an obvious way to delete parts of it.

Similarly, in another thread (https://forums.comodo.com/comodo-cleaning-essentials-killswitch-autoruns-cce/how-do-i-unblock-a-processexecutable-t84489.0.html) someone suggested that “This can also be achieved automatically in CB by using macro feature in backup step 3 with the option to reset the macro every 7 runs.” I’m afraid it’s not obvious to me how to reset the macro every 7 runs.

Suggestions welcome.

Many thanks.