Stemming from a mention in Steven Furrow's independent film, "Clock Knockers," the term refers to both 6:28pm and June 28th. 6/28 is the official day for having sex with two women at the same time - a play on "pi" equalling roughly 3.14, which when doubled equals "6.28" (pi being a pun for "pie," which is slang for vagina).
Legend has it that any man has the power to achieve the ultimate goal of 628 on 6/28, with 6:28pm being the perfect time to make the move.
Lunchbox, an overweight and downright ugly independent wrestler in Florida, was the first to formally celebrate 628. Nobody really believed he could do it, but sure enough, at 6:28pm he made his move and woke up at 6:28am with the biggest smile ever on his face... and herpes, he woke up with those, too.