Pivot Table help! add values instead of count occurences

Hi there,
I could really do with some help with Pivot tables. I am just learning. I have a load of columns, some of them contain text, which in a pivot table I am trying to count the number of times, for example, that apple appears in a column. But some of the columns contain numbers already, and when I drag this field into the Sum VAlues it seems to count the number of non-blank cells in the column, rather than adding the actual numerical values. I am using Excel 2010. I have clicked "sum" in the Summarize Valus By button in the Ribbon for Pivot Table options. But It doesn't seem to work! Any help would really be appreciated.