For example, when I, and, I assume, you click on my avatar to the left it contains, as of a few minutes ago:
Posted 15 hours agoJoined Apr 8, '15Read 1d (1d recently)
(Lack of punctuation or spacing in the original. Actually, the block quote is what it looks like to me in the pop-up. When I copy from the pop-up and paste it here I get different formatting.)
What does “Read 1d (1d recently)” mean?