It is not necessary to have a specific number on each row. The object is to decrease and then form a strap. I have used 6 stitches in the example to make the strap. You can use 8 or 10 stitches for a wider strap.
Row 1: 1 SC in ea SC across, turn.
Row 2-3: Ch 1, 1 SC in ea SC across, turn.
Row 4: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Row 5: 1 SC in ea SC across, turn.
Row 6: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Row 7: Ch 1, 1 SC in ea SC across, turn.
Row 8: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Row 9: Ch 1, 1 SC in ea SC across, turn.
Row 10: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Row 11: Ch 1, 1 SC in ea SC across, turn.
Row 12: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Row 13: Ch 1, 1 SC in ea SC across, turn.
Row 14: Ch 1, 1 SC in ea of the next 2, SC DEC in the next Stitch, turn.
Strap
Row 15 - 30: Ch 1, 1 SC in ea SC across, turn.
Work the crochet button first to make sure it will fit through the button hole.
ButtonHole on Strap
Work an even amount of single crochet on each side of of the strap.
Side 1 Row 31-34: Work 1 SC in ea of the next 3 stitches.
Side 2 Row 31-34: Work 1 SC in ea of the next 3 stitches.
Join with a slip stitch at the top to the opposite single crochet. Slip Stitch across to the edge. Turn.
Row 35-36: Chain 1, Work 1 SC in ea SC across.
Crochet Button
Work the magic circle or a chain 3, join.
Round 1: Ch 1, work 6 SC in the loop or chain. Do not join and work in a continual round. This will be working the first stitch in the top of the first single crochet.
Round 2: Work 2 SC in ea SC around.
Round 3-5: Work 1 SC in ea SC around.
Weave the tapestry need through the last round of stitches, pull to close the back. Sew and knot the back of the button.
Sew the button to the place you want it on the towel.