I believe you can do it either way, the system will use the most specific mask you may have defined. As a third option you can also do:
1 100-149,151-199 4444444xxx
2 150 5555555xxx
Remember you'll need to add the 2nd index to your digital trunk, and reload the card to get the updated existing index to update on the card itself.
Of if your software version supports it, use the Associated Directory Number form to define a specific CPN sub.