KAR - my DS4 is a hider too, about reading (laughing at your "slipped" comment)! So we don't really know exactly when he met milestones.
Counting - could count to 20 by 2.6; one to one counting, just before 2; simple adding, by at least 3.6
Reading - signs/road signs between 2 and 2.6. Beginner books - since he's a hider, not sure, but at least by 3. Days with Frog and Toad, just before 4th birthday.
By the way, many of you have probably seen this, but SENG does have a pamphlet that they would like pediatricians to hand out:
Seng gifted pamphlet 
