I noticed that bottom attached buttons on cards look off by two pixels, one on each side. You can check that at the official docs but where is a screenshot (Chrome):

I'm not sure what's the purpose of these rules, but they are the ones breaking it:
/* Buttons */
@buttonMargin: 0px -@borderWidth;
@buttonWidth: ~"calc(100% + "(@borderWidth * 2)~")";
What's the official take on this?
Thank you!