Based on the picture you provided, I would suggest that, if possible, you should use holes that will allow your lag bolts to go through the horizontal band of wood and the vertical post portion, as well. This will give your bolts the maximum about of solid wood to grip into.
It's hard to tell from that image, but I would suspect that you used 1 by material ...
Most likely it does not matter, which is why they give you multiple holes, so you have some wiggle room with centering on a wall etc.
But the only way to know for sure is to look at the instruction for your specific TV mount.