"number of weeks collectively that those songs were on both charts at the same time"
Just to make sure I've got the second number right: first number is number of songs that overlapped at number one. But is the second number the number of weeks such songs overlapped at number one, or is it the number of weeks the relevant songs overlapped on the charts (i.e., for the songs that hit number one simultaneously, this totals the number of weeks song A is on both *charts* somewhere between 1 and 40 at the same time, song B is on both charts between 1 and 40 at the same time, etc.)? Your *words* seem to be saying the second, though I was originally assuming you meant the first.
"number of weeks collectively that those songs were on both charts at the same time"
Just to make sure I've got the second number right: first number is number of songs that overlapped at number one. But is the second number the number of weeks such songs overlapped at number one, or is it the number of weeks the relevant songs overlapped on the charts (i.e., for the songs that hit number one simultaneously, this totals the number of weeks song A is on both *charts* somewhere between 1 and 40 at the same time, song B is on both charts between 1 and 40 at the same time, etc.)? Your *words* seem to be saying the second, though I was originally assuming you meant the first.
It’s the first one —eg in 1992 there were 10 weeks where Whitney Houston was #1 in both countries at the same time
I think I missed a “#1” in the description, have added that in