If I understand it correctly Attributes can go over 10. In fact, in the game I'm currently playing if I arm a Ranged Weapon my Perception stat goes up to 11 (the base of which is 9).
The 'Gain Attribute' perks are limited to 10 however. If you have 10 points or over, they shouldn't be selectable. That applies for my Perception stat currently, so those perks should be correct. As for the other perks that increase stats those don't mention any limits so I assume those can be taken at any time. Quite a handy way of getting around the Gain perk limitations.
And the sentence you've quoted there, Fljotsdale, just refers to the Gain perks- it's impossible to take the perk when the stat is 10+.
As for the 15 limit, I don't know, I've never managed to raise a stat that high, generally my stats are at 10 or lower.