1) I think you cannot delete cells in tables you typed/copied with "instert/data". So you could copy just the data (without the column headers and without the last two lines with zeros) to a newly created table and use this.
2) Another way would be to follow your creation of data with Data:=submatrix(Data,1,17,0,1) to copy just the data needed and store it again in Data.
3) As I understand you have to examine more than this one set of data, so you might consider using the READEXCEL() command to directly read the necesary data in your matrix Data. See attached (both files have to be in the same directory).
