How much adblue did the MFD recommend? I ask as I was down to 600 miles earlier in the week so topped it up at the pump in a garage near home. IIRC, mine said a minimum of 1.25 and a maximum of 2.25 gallons (ie. roughly 5.68 to 10.23 Litres). I put 9 Litres in, paid at the till and when I switched back on it was telling me that I had 5500 miles in there (I expected more though) - that should easily do for a month on the road starting Sunday. I purposely didn't fill to the max recommendation as I'm conscious of reports about people overdoing it and the system not resetting.
When the 650 miles error comes up it doesn't suggest any amount to add, it's telling you there's something wrong with the system and you've got 650 miles to sort it out.
Bit of a minefield to what it can be as well, sometimes it goes away by itself, sometimes it doesn't!