The resolution is simple. Add only the numbers of "curls".
 
The digits 1, 2, 3, 4, 5 and 7 counts each 0 curls.
The digits 0, 6 and 9 counts each 1 curl.
The digit 8 counts 2 curls.
 
Consequently, the resolution for 2581 is 2 (curls).