PrecStep is the number after the number of bits of the indexed value begins with a new term. The initial value is always indexed with complete accuracy. Accuracy step 4 for a 32-bit value (integer) means terms with these bit values: All 32, left 28, left 24, left 20, left 16, left 12, left 8, left 4 bits of value (total 8 members / value ) The exact step 26 will index 2 members: all 32 bits and one single member with the remaining 6 bits to the left.