sumif does not work as expected

[BlockEnthusiast]

under menu options

Help > Function List

it shows the syntax of SUMIF as:

SUMIF(A1:A10, ">20", B1:B10)

However I am finding that this formula does not work as expected.
In the below image I tried this formula and managed to get 3 distinct outputs

I had tried changing all formatting to number and that still had these three distinct outputs.

I want to preserve this sheet for reference, so tried to duplicate the sheet.

• This created a second sheet (sheet 2).

• Until i clicked on sheet 2, i was still on sheet 1, it showed the screenshot above

• When I clicked on sheet 2, I saw all the values were NaN

• When I clicked back on sheet 1, I see all values are now NaN instead of whats displayed in screenshot

• Using control Z can bring back the original outputs.

• Setting global cell format to number or automatic had no impact.

• Clearing format globally "added" the numbers together as strings like:
  (300003000030000300003000030000)

• Setting everything back to a number results in NaN 0.0