microsoft.excel.courses.in.london - Excel

Hi

In the right hand corner of the bottom tool bar of excel when you click on a column Excel usually automatically calculates and shows the "sum" of that column when populated with numbers - Excel is currenlty however showing the "count" of the column, not the "sum" - can you please tell me how I change back so that Ecel automatically "sums" rather than "counts"

Cheers
NICK