Every source for instancing parameters must have the same number of values.
In your file you use the SOP null_t’s point position to control the offset. When you middle mouse click onto the SOP you can see that it has 9088 points (the rows*cols in the grid SOP).
You also use the TOP null_texcoord as a source and this TOP has a resolution of 1280 x 692 resulting in 885760 pixels (or values).
So there is a large difference between the 9088 points of the SOP and the 885760 pixels of the TOP. Hence the error. I think the misconception is that the Size parameters of the grid SOP, are not equal the data. In SOP space this is really just dimension. A rectangle with 4 points could have a size of 1920x1080. So you would want to match the Rows and Columns of the Grid SOP to the resolution you intend to use of the TOP.