I know how to use a calendar, do you? There are 4 weeks per month. Wed and Sun = 2 times per week. 4 x 2 = 8 Some months actually have a partial 5th week, hence the additional day or two. 8 + 1 = 9 and when it does include both an extra wed and sun then it would be 8 + 2 = 10. As an example last month had 4 sundays and 5 wednesdays = 9 so they would have met 9 times that month. May and June both would have given 9 meeting days. May having 5 sundays and 4 wednesdays. Actually there are a lot of months with the extra days making it more likely that they were meeting 9 times per month and not 8, with 9 being the middle of 8 - 10.
Do you need more information than that.
“...when it does include both an extra wed and sun then it would be 8 + 2 = 10...”
Show us a month in the last 100 years that had 5 Sundays and 5 Wednesdays.
“Do you need more information than that.””
Yes.
The article states the meetings were held on Sundays and Wednesdays. In order to have 10 such meetings in a month, that month would have to have 32 days.
Are you sure your expertise in using the calender is as polished as you claim?