Sunday night, Demi Lovato shared a photo of herself and longtime boyfriend Wilmer Valderrama on Instagram, along with a short and sweet caption: "6." While it initially seemed as though the digit signified an anniversary , it turns out that Lovato was just marking the day they'd met.She also recently cleared up a little mystery around her early days with the That '70s Show star — and how he had some reservations about getting together with her in the first place."He had some hesitations," Lovato admitted, mainly surrounding the sizable age gap between the two. The famous pair are 12 years apart; they met when the singer was just 17. "Once I got older, we could be together," the "Confident" singer explained, adding that Valderrama is her "best friend."The now 23-year-old also demystified a rumor swirling around the romance as of late: The couple definitely did not secretly marry. As for when they will be tying the knot, Lovato said she has "no idea." Any interested parties will have to ask Valderrama for specifics on a future engagement, she added. Anyone else sensing a hint somewhere in that comment?