public int flipbookColumns { get; set; }

When Unity imports a texture with a TextureImporterSettings.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 TextureImporterSettings.flipbookColumns and TextureImporterSettings.flipbookRows settings.