Definitely looks like a rounding problem. What you see may look like 1.6,
but internally it may be something like 1.5999999999999999999999999. For
display purposes, Excel would display 1.6.

Accountants run into this a lot when they use formulas  to calculate monetary
amounts and then add the columns of numbers. What is displayed may be
correct to the last zloty, but in fact contain fractions, that are not
reflected by the cell format.

How are these values calculated?