I've noticed the most protractors have the numbers running both ways. For example, if reading from the left side to the right, it may show $0$ to $180$ and $180$ to $0$.
Does it matter or how do you know which direction to read the measurements? For example would an angle that looks like this _\ (sorry for the poor drawing) be measured as, say, $40$ degrees or $140$ degrees?
See in the picture below how you estimate the angle looking like _\
As a rule of thumb, an acute angle is always smaller than 90 degrees, whereas an obtuse angle is always between 90 degrees and 180 degrees. The angle below is therefore approximately 45 degrees.