Question about fence pixel constraints

[amimods]

Hi! I'm new to stardew & modding in general, I'm trying to make a fence as my first mod  As I understand it I just draw over the original fence image with the corresponding parts, but do I have to exactly draw within the pixel size of the parts/images within the fence asset? Or do I just have to make sure there is empty space between them, a few px taller or wider won't matter? I'm struggling to make the fence symmetrical in a way that I like within the width constraint right now  The image allows for 6 px wider before it touches the next image, but that goes outside of the original drawings width. Thank you!