From what I understand, if you get a new device and install Waze, it may or may not show your existing score on the client, and may start you over at zero. I don't know if this will eventually try to catch up, or what.
I've never seen the scoreboard on the phone higher than the dashboard on the site, but it could be whatever they were referring to with the scores being delayed last night. I did my nightly entry into my spreadsheet last night and it looked pretty accurate to me.
Now, the dashboard, and the top 50 list have had a discrepancy of about 3000 points for the past month or so. I know someone else mentioned that on the forums too. That may have something to do with it too.