Usually, the instructions in the parenthesis indicate how many pieces you need to cut for different sized quilts. Somewhere in the description the different finished sizes should be listed.
For example, if the directions for your quilt include a lap, twin and queen size, than 2 (5,10) 2-7/8" strips, cut into 20 (64,132) -1-7/8" squares means for a lap size quilt you would cut 2 strips that are 2-7/8 wide, the cut each strip down into 2-7/8" squares.
For a twin-sized quilt, you would need 5 strips, and 64 squares total, and for a queen size, it would be 10 strips, and 132 squares total.
Good luck!