Excel uses a 5 digit number to represent dates so that it can do calculations...

today's date, for instance is represented as 43166. (to see this enter today's date in a cell, then format it as General).

Now 43166-0 = 43166 and 43166+1 = 43167 which when multiplied by 10 gives 431670..... so there should be a date of some kind in column K.