If you want to explicitly enter 16th notes, you have to make it obvious to StaffPad that that's what you want, otherwise it can interpret the lines as 8th or 32nd notes, or a combination of those depending on where the notes fall in the measure. Again, for simple scores where the handwritten music is fairly obvious, it works fine. The key point is that the entry method slows down professional users, because you have to make sure you're doing things that the program can understand, which means taking time to place your marks methodically and reviewing every entry you make to make sure the program was correct to your intentions.