Because this is exactly what I thought when I began playing and I'm assuming you're having the same problem, when people say numbers for move inputs, they don't actually mean the numpad - just the direction, as if you were using the numpad. 2 is down, 6 is towards (not right), 3 is towards and down, etc. There's no actual button for diagonals - they just mean both buttons together.
I've had to explain that more than once and I have yet to think of a good way to phrase it so I hope I didn't just confuse you more.