Mutiturn encoders typically use 12 or 13 bits to keep track of partial turns. This means to find the number of turns you just need to shifth the counts right
turns:=Shr(Counts,13) ;
In some cases you may want to use a count offset
turns:=Shr(Counts-CountOffset,13);
In these examples I am assuming that there are 13 bits that indicate the position with a turn.