How do i change the column type in Numbers from number to string

Use SUMIF instead of COUNTIF. SUMIF let's you search for a value in one range and accumulate values in another range if a match is found. COUNTIF counts the occurrences of a match, which is why you're getting lower than expected results.

Let's say I have two columns: Type and Count. Here's our sample data:

If I want to SUMIF all the Count values when Type is value A I'd use:

=SUMIF(A2:A7, "A", B2:B7)

Doing this for values A, B and C yields the correct results on our simple data set so we can convince ourselves this is what we actually want:

So, in your case, you'd want to do something like:

=SUMIF(<range where you keep gun type>, "Pistol", <range where you keep shots fired>)

And that would give you the total shots fired any time you recorded the gun type as Pistol.

Note, it's not necessary for the columns to be adjacent, which is nice. But they should have a similar range or odd things can happen.

This admittedly is a bit of a hack but I can't find another solution that works in Numbers.

One way to make letters appear over the numeric values is to position textboxes with the letters over the values to block out the numbers below them. Just click the Text button in the toolbar, drag the textbox to the correct position, size it appropriately and set it to have a white fill colour and no border.