I received a request to route a percent of calls (say 15% for an example), that are in an inbound flow to a DID transfer point, would this be accomplished possibly by an expression, if so what would be a possible expression filter? Am new to the concept of flow expressions, thank you in advance.

Random() <= 0.15

If true, route your calls to the transfer.  If false, do whatever you want the other 85% of the time.

https://help.mypurecloud.com/articles/architect-expression-help/

I received a request to route a percent of calls (say 15% for an example), that are in an inbound flow to a DID transfer point, would this be accomplished possibly by an expression, if so what would be a possible expression filter? Am new to the concept of flow expressions, thank you in advance.