Your target gauge equals about 4 stitches to one inch and 1-1/2 rows to one inch. Before starting the poncho, first make a gauge square using the #7 hook (between a G and an H) recommended or a larger hook if you crochet tightly.

1. Chain 24.
2. Follow the pattern and crochet 8 rows.
3. Lay the resulting square flat and square it up. The fabric should look like the fabric in the photo of the poncho.
4. Measure the full length and width with a ruler or steel tape. It should measure about 8 inches wide and 6 inches long.

Using Cat 4 yarn and a #7 hook, you should be in the ball park on size--no more that a couple of stitches or one row off. What could make the line count too small? If you're pulling the yarn too tight when making a stitch. If you're not smoothing the fabric out on a smooth surface before measuring. If you're using a size 7 *steel* hook instead of aluminum (a long shot, but I'm sure someone has done this at some time).

If you need to go to an H hook, make another swatch to check your gauge. Repeat if necessary until you have the right gauge. You can reuse the yarn from the first swatch one or two times, so you might want to go to another fresh ball for the second swatch. When you get the right hook size and are ready to start on the poncho, re-use the swatch yarn.