Dickies Women's Long Sleeve Cotton Twill Coverall

The size chart makes no sense... it lists american sizes (12, 14, etc.) but the sizes are in med-large-xlarge etc. so this information isn't helpful?

I am 5'8" and 135 lbs. I need these to also fit over clothes so what size should I get?

I'm confused on the size chart. it specifies inches for sizes in 4, 6, 8, etc. but when you go to order an item, it's xs, s, m. is a 4 a s or xs?

I am 159 cm which one should i take? M or S