There are 7,8,11,13 windings in tzizit. There are always 2 halves: Do these count as 1 towards the number?
There is also a shita that holds the windings are 10,5,6,5. Can you explain this shita, and can it be used lachathila?
1. There is some discussion among poskim as to how to treat the halves. Orchos Rabbeinu writes that the first half combines with six complete revolutions and with a final half at the end, giving seven. Others write that one should not count the half at the beginning. However, in general the idea of the numbers (7, 8, 11, 13) is that the knots should look like they possess 7, 8, 11 and 13 revolutions, and for this purpose, I think doing 7.5, 8.5, 11.5, and 13.5 is preferable (as ruled also by Ozer Yisrael, 11, note. 104).
2. The shita you mention is practiced by some Sefardim, the numbers representing the Great Name of Havayah. This is not the common custom and should not be used lechatchilah by Ashkenazim.