It is displaying multiple rows because there is a data value that is different in each row. If they were identical it would only show one time.
So one approach would be to eliminate the column that is causing this if you don't need it. Or if it is a date time field get rid of the time for example. Again, if you don't need it.
The other thing that might work is to do a Distinct based on a field in an expression or in your Dimension.
I would need to see and understand your data a little better to know for sure.