Preventing Value Increase When Filling

I am using Excel to maintain a database for a computer game I'm playing. One of the things I'm using it for is to keep track of wages that I'm paying in the game. I do this by keeping the total potential wages in one column. As I only pay an employee when I use him, I then copy the wages over to the next column, where the total actual wages per event is calculated. However, when I copy the value from one column to the next (using the lack cross on the bottom right corner of the cell to drag it to the next) the value sometimes increases by one each time.

This isn't a major annoyance, but I'd like to find a way to prevent it happening at all. Does anyone know how to stop the increase?

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A related issue that I experience is that sometimes when I copy or input a value in these columns, it brings up an error message saying "Number Entered As Text". Is there any way I can prevent this? Both these issues occur apparently regardless of formatting, and only on some of the cells, so I don't know quite why there's any problem at all.