Query Re- Tumble

[LordCove]

Hi, quick query regarding tumble - I read about it, but need it simplified.

Every 5 points in Tumble grants a +1 AC

Say I have 13 Tumble, and equip some leather which gives a +3 to Tumble, making 16.

Because the Item has increased my Tumble, do I then gain a furthur +1....

...cause if so, it aint working.
and if not, it is working.

Thanks

[Pankoki]

It's working as intended. Only actual points spent in it count for AC purposes, the rest is simply for skill rolls to avoid AoO.