TI home 2009 edit scheduled task: change "Create full backup after" not working next start task

Following:

Rightclick scheduled task --> Edit --> Backup method --> Change "Create full backup after" value.

This value wasn't set correctly and a smaller parameter was set. I expected next day backup to take a full dump, which it did not and continued taking differential dumps. Only way is to creating a new backup task in order to set the correct value.
Does this mean you can't edit your scheduled task and always have create a new backup task?