GIMP :: Adjusting Default Values For Brushes?

Im sick of writing the value of brushes i want to use like example: brush size 10 or brush size 20 or brush size 5 or less..

Whenever i touch to adjust brush size by mouse it always is like this: brush size 334 or brush size 554.. Why it is so easy to pick 400size brush and almost imposible to pick 40 size brush?

Brush are? its like 500px wide.. since when small brushes are obsolete?? i never use bigger brush than 50! and most of the time i use brushes that are less than 10(value)

So its pretty important for me(i hope not only for me) to easily pick small brush sizes..