Brian 110 is the fan angle/size of the jet and the 015 is the oriface/hole size of the jet.
The usual guide is that the total jet flush size is 6, so if you have 4 jets with a size similar to the above jet of 015 then you have a total of 6. If you had a 2 jet wand then you would have a jet size of 03, so 2 x 03 =6.
The fan width ( the 110) for a two jet wand would be right but for a four jet wand you would need small fan spray widths so you would use a 80 or 90 degree jet. One a smaller tool such as an upholstery tool you would prob use a 60 degree jet.
Basically the bigger the end number( the hole size) the more water you are going to spray out. Some truckmounters give a greater flush because they can suck the water back quicker and believe it or not actually give you a drier carpet, for example i have an Evo wand that has 6 jets and i total it up to 9. That gives me great flush and because of the vortex with the 2inch bore gives me a drier finish.
Hope that makes some sort of sense.