Are you perhaps struggling with the concept of relative units? Specifically em in this case?
I'm not 100% sure what your question is here but to explain a little -
Your "home" is an <h3> which has a default margin of typically 1em top and bottom making the margins equal to the font size - the font size doesn't get "added" precisely but since the font size is 90px and the margin is 1em it follows that they're 90px. As your font size changes do too will your margins.
In the case of the home score you have a bottom margin because it is specified in your p block...
You've set a margin-block-end: 1em; Once again, since the font size is 90px then the bottom margin (the block end) will therefore be 90px.
There is no top margin in this case because you have set it to 0px as part of the .zero definition.