Using the Numbers app, how to make 2 plus +0.25 become 2.25? When a row in a table from a webpage is copied to the Numbers app, such as

2       3    4      5


and another row is copied, as some "deltas" (minor addition or subtraction):

+0.25   0    0   -0.5


Then the numbers are added up vertically.  The number in the first column adds up to 2, while the last column adds up to 4.5.  So the first column is incorrect, and the last column is correct -- I think the reason is +0.25 is treated as a string, while -0.5 is treated as a number.

Is there a way to make it work on Numbers?   (manual editing is not preferred, as it is error prone and there are actually a lot more numbers, and finding the + by eye and removing it can cause an error when it is not seen, and if there are 200 such numbers, then doing it 200 times by hand is quite a time consuming method.)

(and actually, this happens on Google Apps as well)
You can use the Search/Find functionality (Cmd-F) in Numbers to replace the + with "nothing". Don't worry about + in formulas, they won't get replaced. Summing the the rows should work ok afterwards.