The carriers are sized using lines and dots. Each line represents a 1 and a series of dots represents 0.5. Eg; 2 lines and dots equals size 2.5. Carriers range from size 0 to 3.5 but most people only have from 0 to 2.5 and most new kits have even less.
When tuning your level 10, remove all the shims from the powertube before starting. They don't affect the operation but they can cause false leaks which cause you to use a carrier size that is too tight. Don't put them back when you are done. You shouldn't ever need them.
For carrier sizing:
Find the carrier size that causes the installed oring to fit freely over the bolt stem. The carrier should sit on the bolt stem without moving if the bolt is held in a vertical position. If you tap the valve on a hard surface, the carrier should be loose enough to allow the bolt to move. If you have to force the carrier onto the bolt stem with any force at all, then it is too tight. Install the bolt and valve into the gun. When aired up there should be no leaking. If it leaks, take the carrier out and replace it with the next smaller size. Always use the same white carrier oring in each carrier that you use. It is the oring that you are adjusting. Try it again. You want to use the largest carrier size that does not produce a leak.
Any time that the gun fires and does not reset or short strokes and does not reset, or just chuffs and does not reset, the problem is most likely a carrier that is too tight. Installing shims will not help. Shims only help if the bolt moves, hits an object but does not vent any air, and then cannot reset because the chamber is still fully charged. Most of the time the bolt always moves far enough to expose the vent hole, get rid of excess air, and then reset.
For spring adjustment:
You want to use the bolt spring that allows you to shoot about 20fps above the lowest velocity that the gun will cycle at. So, if you want to use the gun at 280fps, then your desired lower limit of operation is 260fps. Insert your long bolt spring. Turn the velocity adjuster down before you air up the valve. Then gradually turn up the velocity until the gun will cycle. This is your lower velocity. Measure it. If it is above 265fps, then you will need a shorter spring or you will need to clip the one you have (unless you have red one. They are usually in the correct range). If you clip a spring, only clip half a coil at a time and then try it using the same procedure of starting with a low velocity setting. Make sure you put the cut end of the spring towards the bolt. If you have the short spring installed, and the lower range is 30fps below the desired shooting velocity, I wouldn't worry about using a stiffer spring and would just go with the short bolt spring. If it was much lower than that, I would definitely clip a long spring to get closer to the desired range.
Except for the Automag in front, its usually the man behind the equipment that counts.