No, she meant the she thought September and November where consecutive months, she forgot about October.
Alex was trying to explain the knuckle method of remembering how many days there are in each month, which after Adele confused him he decided didn't work, but it does.
Start with the knuckle of your smallest finger on your left hand, that's January (31 days) the space between that kunckle and the next is February (28/29 days), the next kunckle is March (31 days) the next gap April (30 days) etc. All your knuckles correspond to months with 31 days, the gaps to the others. After July (knuckle of index finger on left hand) you have to swap to the other hand (knuckle on index finger of right hand) as July and August both have 31 days.
Simple!!!!
Adele forgot about October!