For this font basically everything is roughly 7px in heigh. The decender or ascenders might go past this a touch.
8 is the factor you can scale by using the .ttf that still maintains the fonts correct visuals while increasing the size. The program I use I have found works best when using incruments of 8, 16, etc.
I should probably include information on these about ascender and descenders.
Hope that helps, cheers!