Custom texture atlas scale

Hi everyone. I have problem with custom texture scale. Main idea it is the scale custom part of texture atlas by scale UV coordinates in Vertex Shader (look at attached.jpeg). And it works in pixel shader, but don’t in vertex. I suppose reason is fraction node because it don’t return 1. When I start scale part of texture atlas it give unpredictable result (look at Example.jpeg). If you know how to correct it, please tell me.