Bat Familiar Fly Skill

[Minigiant]

So I put my hands up and say I am still learning the finer points to Familiars

I am currently in the stage of reverse engineering the skills for the creature. I have chosen Bat and I have found some math i cannot seem to figure out and am hoping some kind person here can help me

It says the Bat has a +16 Fly skill

To me that is +10 from having a fly movement speed, and +6 from its Diminutive Size.

Put what about it's DEX of +2?

Shouldn't that mean its Fly is +18?

[Taja the Barbarian]

Fly Skill

+4 from Good maneuverability
+6 from Diminutive size
+1 from 1 skill rank
+3 for being a trained class skill
+2 from Dexterity 15

Grand total of +16 to Fly checks.