Hey Mauricio! Thanks for reading. For clarification, do you mean the bounding box, or a container you’d design as a box around your type?
If it’s the bounding box, that doesn’t matter — you’d want to align the bottom of your letters with your baseline. Setting your line height to a multiple of the baseline makes this easy peasy.
If by box you mean a container that you’ve drawn around your type, then both elements should hit the baseline. So, for example your container height would be a multiple of your baseline (say, 700px for a 7px baseline) and the type within it would have a line height that’s a multiple of your baseline height.
Hope that helps clear things up!