2nd Monday cume less 1st Monday cume, added to second Monday cume is approx delist.
One half of (3rd Monday cume less 2nd Monday cume) plus 3rd Monday cume is approx delist.
Obviously, this is very rough, but you can do it in your head
Example: MOVIE has opening weekend 45; second Monday 79; third Moday 97
MOVIE did 45 first weekend (adjust 121.50) , and is at 79 after 2nd weekend. (79-45)=34 and 34 plus 79 = 113 (Not great legs)
Third weekend less 2nd is (97 - 79) or 18 and half is 9........ 9+97 = 106
Veeerrrrrryyy approximate but gives a fast ballpark. Mon-Thurs is built into the approximation.