Sorry, I am terrible at explaining sometimes! I only clip the two that look like regular claws (the two outer ones).
The ones I don't clip are the two fused/grooming nails, those are the two that are closest to the nail-less "thumb". So, if you were to count the toes starting at the thumb on the hind foot, the fused grooming nails would be 2 & 3. Those can look really sharp but since they use them as a "comb" I don't trim them. I haven't noticed those ones getting caught on any fleece in my cage, regardless of their length. The nails on toes 4 & 5 get trimmed every 2-3 weeks in my house. Hope that helps!