Dome light in owner's manual
(page 12-16) is listed as 12V-8W but no bulb number.
Pert on the Subaru parts website is here:
part numbers 84920AC050 ; 118650021; 684102090; 784920330 [these are NOT industry-standard bulb numbers]
2014 Subaru Crosstrek Premium 2.0L CVT. #84920AC050: BULB-ROOM LAMP
According to the Osram Sylvania website, the industry bulb number is: