In addition what the others said, the number usually indicates how many layers of carbon prepreg where used in the construction of the spar.
2PT 2 layers,
3PT 3 layers etc
Other manufactures generally use a different naming scheme, Avias is especially confusing. Since for Avia a SUL spar is heavier and stiffer then a UL spar
Dynamic simply uses the design weight of the spar for its name Dynamic 12T, Dynamic 9T for example. Aerostuff is another animal, Gold, Silver, Blue, Zen, S. And Revolution names their spars once with a logical system, but lately more and more new spars came out that just have a catchy name. Zen, Race, Greenrace, SLE, 2 wrap, 1.5wrap. 3 wrap. 4 wrap.
Pultruded spars usually are just named by the manufacturer with the diameter and maybe a designation for the wall thickness. Excel 6mm Cruise, Strong, Structil 4mm, Avia 0.2300 etc.