Note:
Beg ch 2 does not count as a st.
I did not need to add extra stitches when increasing the number of rounds. My coasters are not very tight or loose. It laid nicely flatten. I thought it would be looser and get a spiral edge if I added extra hdc stitches in each round. If your coasters got a tight a lot or got a spiral edge, add extra hdc st in ch-2 space you crocheted one hdc in rounds 5 to 8.