Sorry for resurrecting an old-ish post but it seems like the original poster is confusing _frames_ per second with _fields_ per second.
The “30” in 30p is referring to _frames_ per second.
The “60” in 60i is referring to _fields_ per second.
Both the “30” and “60” are actually rounded off numbers. They are actually 29.97 and 59.94 respectively. I guess marketing decided that “30p” sounded better than “29.97p”. 🙂
2 fields makes up 1 frame. So two 59.94 hz fields is in fact one 29.97 hz frame after deinterlacing.
So Premiere is correct – 30p and 60i are both 29.97 frames per second.