unknown format

I have some data from my friend, first column is the time as ex. 01:02:59 and second is number ex. 5 once i will create pivot table and than want to group the time to be sorted by hours (between 01:00:00 and 01:59:59) will jump a error CANNOT GROUP THAT SELECTION. am not sure why ... also the time in original cell is in unknown format, is on left side of cell and if i will double click on the cell the time will jump on right side of cell. If i will double click on all of them it and all of it will be finally on right side of cells it will works for grouping and than sorting by hours... it looks like is in some format but i can not find in which one or what's wrong...

format.xlsx