Norton Ghost 15 recovery points

1.  During the backup set up  procedure (Norton Ghost 15) there is an option to set the number of recovery points.  What determines how many recovery points should be set?

 

2.  I assume that Incremental backups contain changes that have occurred since the last backup.  What if the incremental backups contain malware or corrupted files?  If a backup recovery is made will the incremental files be added and thus introduce malware and corrupted files etc to the recovered backup?

 

:smileyfrustrated: