The measurements on a try square start at the far end of the blade. Why? Wouldn't it be better to have two measurements starting at the 90 degree angles like a framing square? Or was a try square never intended for measuring, just trying? The lip on the stock is so handy though.
Rule markings on a try square are not a standard thing. Most of the try squares I've seen don't have any rule markings at all. For example, this try square has none:
Combination squares do have rule markings. And like try squares, they also have a lip on them. The rule of a combination square (the metal bar part with measurement markings on it) can be flipped around, so the rule markings can start at either end of the square. Here's an example of a combination square: