VMWare resource limit clarification

Hello all, I am currently looking deeper into the VM resource limit settings on NBU 7.5 and have a question on the following resource limit:

DataStoreType.  The documentation states that the value is "The maximum number of simultaneous backups per datastore type".

It looks like you can only put a number into the value field. 

Question is, how can you differentiate between the datastore types ?  Because the way it looks now, since you can only set one number, then the setting applies to all datastore types.  And if that is the case, why wouldn't one just use the "Datastore" resource limit.

Thanks.