Reflection result divided looks like 'Grid'


I made Reflect inside water material.

It looks good. maybe. but

When see in level editor, Water surface reflection divided looks like grid.

I found affect this view. When change ‘Screen Percentage’, that Girds are moving.

But i not want look reflection view like grid.

Why this situation occur? and how can solving? I want just clean reflection view. not grid.

Sorry about my poor language. thx.