Well, as I understand it, the shell pattern requires a repeat of 3 stitches: you need enough chains to make a certain number of shells ( 3 chains for each shell) in addition to the first 2 stitces you skip before making the first shell. We do not know how many inches wide the afghan is, but I like to make big baby blankets, so I would do about 38-42 inches. How many stitches per inch in the guage for the pattern? Do the math, make the base chain a number divisible by 3 with 2 left over. Then proceed following the directions. And I just keep crocheting the baby afghan till it looks like a nice square shape, which is the best shape for swaddling a baby. Did I explain this clearly? If not, email me or ask more here.

Thank you for the help. I will give that a try.