The manual actually says "Approx 3.0l, with filter change". I've done two oil changes on the bike now, each one took almost exactly 3.25l to hit the middle mark following the instructions exactly as written. The manual also says that the difference between the low and high marks on the dipstick is 0.5l, so this falls in line directly with everyone's reports of their dealers filling to the lowest level, since that would apparently be 3l, or exactly 3 bottles of oil BMW branded oil (sold per litre).
I buy the BMW branded oil from my dealer because it's the same price as anything else I would use. The first oil change, they sold me 4x 1l bottles. The next time they asked if I needed 3 or 4, so I think they know that it takes just a hair more.