You could try something like this:
Code:
p {margin-bottom: 1em}
Doesn't matter much where as long as it's below the initial definition.
Alternatively you could just alter the relevant line(s) directly, such as line 50 in this case. But then you wouldn't have something you can just easily add to the end as an override on upgrades.
Non-settings files will be overwritten by OTA updates, should you choose to use them.