In your pruning instructions below... where exactly is the part I’m to cut? Can you send me a pic so I can see where? " make sure that when you prune weigela branches that you cut them back to a point where two branches meet.” Read more at Gardening Know How: Trimming Weigela – Tips For Pruning Weigela Bushes https://www.gardeningknowhow.com/ornamental/shrubs/weigela/pruning-weigela.htm
If your weigela is big enough to have multiple branches, then you will want to cut the branches where they meet at the v section leaving just a small piece of branch. If it is still a single stem, or very young, then you can cut down to your preferred height, right above where a leaf is, or was. Even if you do make a cut in the wrong location, it will not do any damage. The guidelines suggest the best way to make it look its best. It won't be dangerous to cut slightly out of place.