“Excel can do strange stuff”

To SUM a column that has data that is not in numeric format. The 'numbers' you are trying to add are Texts, not numbers. When using the standard SUM function the answer will get "0".

1.One option is to combine this in an Array-formula: instead of =SUM(E10:E13) use =SUM(VALUE(E10:E13)) and press CTRL,SHIFT,ENTER (instead of only ENTER).
The result will display as ={SUM(VALUE(E10:E13))} even though you never typed the {}.