"I sometimes come across recipes that call for a #2 can. What does this mean?"
Cans used to more commonly go buy numbered size. Commercial products sometimes still do, but most items you find in the grocery store list volume or weight measures.
A #2 can holds 1 pound 4 ounces, or 2 ½ cups.
A #10 can holds 6 pounds 6 ounces, or 96 fluid ounces, which is 12 cups or 3 quarts.