The number of columns in the source image for a Texture2DArray or Texture3D.
When Unity imports a texture with a textureShape of TextureImporterShape.Texture2DArray or TextureImporterShape.Texture3D, it divides the source image into cells. Each cell is imported into its own layer or depth slice of the resulting texture. You can set the number of cells using the flipbookColumns and flipbookRows settings.