Add the words " as each other" to the end of that thought and it actually makes sense. Something to do with 2 months with the same number of days perhaps? Pick any dates that fall on the same day of the week from any 2 months that have the same number of days and it will be true I think? I haven't tested it extensively but seems to be true.

Don't get it.

On a side note and out if curiosity, interesting abbreviation for the word number. I usually see it as 'No.' Is that a thing in your country/ language?