Why Does Avast want to make changes in my backup files?

I use Acronis to back up some of my files on a daily basis onto my HD. (I also do backups on a weekly and monthly basis onto an external HD.)

When I run an Avast scan it asks me if I want to allow is to make changes to the daily backup Acronis files. This happens only on one of my 6 computers that use the same software.

Why is it doing that?

Hi, post a screenshot.