2 open or empty pages in your pas port is what he is talking about.
When crossing borders some countries require you have at least 2 empty pages in your passport. I'm not sure what Canada's policy is but I just had extra pages added to my passport last year because I was down to 2 or 3 pages and was heading to Alberta for a deer hunt and did not want to find out Canada's policy the hard way.
You guys were really, really lucky and apparently had one of the nice border agents helping you out. I've seen so many guys turned around at airports and border crossings that I don't take anything for granted including myself getting in to Canada the next time I go up there. Before 9/11 it was so much better. Once I actually took a Delta flight but forgot my wallet at home, didn't have a passport or ID and was not given any paperwork from the company whom I was doing work for in Canada. I got a real ass chewing from the Canada customs agent but in the end he let me in.
50 years ago I was just a kid and went to Canada on fishing trips with my parents where I caught my first northern in Flin Flon, Saskatchewan. The memories are a little fuzzy.