7 months...

Glow is saying in 7 months pregnant and I'm 27weeks 1day but I thought 7 months would be at 28weeks. 
4w=1m
8w=2m
12=3m
16=4m
20w=5m
24w=6m
28w=7m
32w=8m
36w=9m
Or am I wrong on how I'm calculating this?