So on facebook there was this thing you can like, I like it, but what does it mean?

Me: Can I use the bathroom?
Teacher: I don't know, can you?
Me: When I was using "can" I was using its secondary model form as a verbal modifier asking for permission, as opposed to expressing an ability. I thought since you were a teacher you'd know that. My bad. MAY I use the restroom?
Teacher:...

Okay it moded the teacher but what does this part mean?
* When I was using "can" I was using its secondary model form as a verbal modifier asking for permission, as opposed to expressing an ability.*

LOL, Thanks(: