I'm hella late to the party (yay Asia timezones), but what it's supposed to show is the number of elemental weapon skills your kamihime benefit from. Click on the blue skill number and you'll see a summary of which weapon skills are active. Which is why I was worried, in an ideal weapon grid your the blue skill section should read skill 9, but since I see skill 4, I was having doubts that your entire weapon grid was fully fire. If you're running a rainbow (or anything close to not full fire) grid, that might contribute to the problem.