I've always thought as long as one day fell between the Mon-Fri.,it was considered an actual assembly week.
I can see June 1968 & March 1969 as having only 4 weeks,but May,Sept.& Dec. both look like 5 "
E" work weeks to me in both 68/69 calendar years.
Here's those calendar years..
http://acs.flicklives.com/Timeline/1966_cal.html
http://acs.flicklives.com/Timeline/1967_cal.html
http://acs.flicklives.com/Timeline/1968_cal.html
http://acs.flicklives.com/Timeline/1969_cal.html