Difference between creating an offset and a write off in PeopleSoft Maintenance worksheet

Hi,

I am trying to create an offset to an item by using the maintenance worksheet in AR. After selecting the customer & Item in the Worksheet selection page, I choose the entry type as Offset an item in the Worksheet Application page. The lines which  want to offset are selected along with type as MT. My understanding is that to match the +ve amount of the invoice that I want to offset I need to select a -ve amount in another invoice. This should be done to bring the balance to zero( Net -0).

This is different from Write Off a debit where we select only the lines which should be written off.