Runs large - Rab Cirrus Hut Boot

I wear size 7 in running and hiking shoes. My foot measures 24cm which makes me a true size 7. I got these hut booties in size Small which is supposed to fit sizes 7-8 (women). These booties run really large. I have so much extra space. The smaller size would probably be better for me even though it's advertised to fit 4-6.