Geneva Blouse Front Placket

I am working on a Geneva blouse. I love the pattern so far, but I’m a bit confused with the front packet. It is 1 1/4” wide, but the center front is marked 1/2” from front edge. The button guide also shows the buttons 1/2” from the edge. It seems like the CF and buttons should be centered on the placket at 5/8” from edge. My apologies if I am missing something obvious. Thank you for your help.