Calc: Why might numbers turn blue?

I am aware this is a basic question but I fail to find the answer myself.

In a Calc column, why might some numbers, but not all of them, turn blue?

image description

I feel they should either be all in blue or all in black.

I feel they should either be all in blue or all in black.

yes - and if View -> [x] Value Highlighting doesn’t turn all of 'em to blue, the black ones are Text and alignment to left is also an indicator that you are dealing with text, unless you intentionally left aligned 'em by direct formatting or by applying a customized cell style

Because you have activated Strg+F8.

Value Highlighting

Thank you!