Below are some descriptions to help you distinguish between these terms.
Try Period - number of days your shopper has to try the items after all TBYB items are delivered.
Typically, we recommend a Try Period of 5 days. This is enough time for a shopper to try their items and decide whether or not they want to keep them.
Try Grace Period - only internal, this is the additional number of buffer days the shopper has in case of a delay.
Most merchants deal with grace period request made by the shopper on a case-by-case basis. We recommend applying your brands existing customer policy for grace period extensions.
Shipping Dropoff Period - how many days the shopper has to drop their sent-back items off at the post office after making a decision in their portal.
As for the shipping dropoff period, we recommend merchants select 4 business days. This is a reasonable time frame to give your shoppers to drop off their sent-back items to the post office.
Shipping Dropoff Grace Period - only internal, this is the number of additional buffer days the shopper has to drop their items off.
An additional 2-business-day grace period is often given by default in the event the shopper needs it. Again the grace period days are only known to you.
For detailed information on how to configure this feature, check out our Knowledge Base Article on Program Configuration Settings.