[Gimp-developer] A strange bug: a 20px brush who has 21px actually

["jEsuSdA 8)" <listas jesusda com>]

Hi,

I just discover a strange bug on Gimp.

If I set a brush size of 20 px Gimp generate a 21px one.

You can see a screenshot here: http://i.imgur.com/de0qYhs.png

Look the Option Tool tab and see the top rule with high zoom to view the 
actual brush size.

¿Is this a missconfiguration, a real bug or what it this?

Thanks.