Bad result when writing a number on a terrain

Hi,

is there a way to paint an image with a good result with a brush size at 1 on a terrain ? My number is realistic only with a brush size at 7-8 minimum (i am using T4M, but i think the principle is the same with the regular terrain?)

Or if it is not, is there an easy way to use a plane and a material, and not cost too much memory/performance for the mobile platform? I would like to paint more or less half of a pitch, so one image of the "zero" and 5 images of each number from 1 to 5 ? Any idea?

Thanks