The grid follows the X/Y coordinate system whereas 0 X and 0 Y are on the top left corner. You can't change that.
The resize thing is a bit tricky. Basically, if you change the value and don't hit enter/return or click somewhere in the ribbon, the values won't update. The tricky part is that in order to see the changes, you have to click inside the layout, otherwise the grid won't update.
So, change value->hit Enter/Return or click anywhere on the ribbon->click inside layout->Done!