I'm checking this on my Lv. 99 Immortal, and it's saying it's increasing Max HP by 6,280. However, the Fantastic Power Hair, which the wiki says increases HP by 1%, is showing an increase of 1,570, which is 1/4th of 6,280, so it seems like this set is giving a 4% HP increase instead.
Topic on Talk:SWAT Set
From Elwiki
o you're right. I double-checked and it says +6280 on my characters as well. I probably mixed up some numbers somewhere. I'll go correct that; thank you for letting me know!