Oh Carole, it's so good to know I am not alone in seeing things back to front!
I am doing the smaller version too and had my calculations all wrong so I only have 100 to do as well. That meant that I only had to redo 1/2 of my chevrons.
It wasn't too difficult really, I just folded them over sewed the line on the opposite side and then ripped out the line of stitching on the opposite side. All done now and ready for next week. Did you save the little bonus triangles? I did and now have a lot of 1 1/2" HSTs. They should come in handy for something, somewhere, sometime.