Block III is an all over mock cable pattern. Cables, mock or otherwise, pull the fabric in differently than other textured stitch patterns do. They often require blocking in order to allow the pattern to relax in to itself and really shine. Until they are blocked they will look smaller than other, more relaxed, patterns. Assuming you've met gauge, you're block can be resized one of two ways: 1. Blocking. Soak your block until it's really saturated, squeeze the water out completely (don't wring it), and then pin it out to the dimensions you need. This will make seaming it to the surrounding blocks easier. 2. Change your needle size. Cables (even mock ones) can really eat up your fabric. Using a larger needle can help with that. When checking your gauge (this block should be 17 stitches and 20 rows for 4 inches), it's important to cast off completely and block the swatch before measuring it. You'll want to make a swatch if you decide to change your needle size so that you can adjust accordingly. I'm sorry that block III is causing you grief but I hope one of the two options here gets you back on track.

Thank you for your feedback on the Knit Sampler Afghan. Everyone knits a bit differently, and our designers do their best to guide knitters so they can create consistent and lovely projects. Sometimes, when knitting items such as an afghan, we often don't take the time to check gauge. For this pattern, the suggested gauge for the Trinity Stitch is 20 stitches for 4 inches. If I use these numbers to calculate the size using 62 stitches, I get 12.4" which is very close to the 12" per side pattern design. In your second comment, Also, noted on 4th row when you’re near the end of row with 4 stitches remaining (K1. P1. K1) P3tog, then K1 (last stitch). This would need to happen with 5 stitches remaining, as one stitch is used for the (K1. P1. K1), three for the P3tog, plus one more for the K1. The four stitches are part of the regular four stitch repeat, and do not need to be called out separately. I understand your experience has been different, and I'm glad you found the other reviewer's input useful. Please do not hesitate to reach out if you have any other questions.