Your counting is right only if there is no decimal involved. In the weird decimal world, 2.6 is greater than 2.18 by 0.42. The number 2.6 is actually 2.60 but the last zero is remove for ease of understanding.
Take a calculator and subtract 2.18 from 2.6, you will definitely get a positive number. Do the reverse and you will get a negative number.
why in the world would anyone use decimals in version numbering? in version numbering there is the first version, the sixth version and the eighteenth version, look at my link on how MacOS is numbered. The same way.