I'm getting "Please enter a valid callback method." error, can't install it too.
I think it will eventually delete all of them anyway but by setting to 10 it will only delete that many at once... this should stop your server becoming overloaded if it suddenly finds thousands of records that it needs to delete, if it only deletes 10 every (not sure how often the cron is set to run) then it is a lot safer! Could set to a higher number though!
Yes and yes