I use a lot of AAVSO charts- I tend to put (AAVSO) after the chart sequence but it does generate a warning that the sequence isn’t recognised but as Gary says, the observations still go into the database and you can review it and see it there.
I also like the fact that the BAA VSS database requires both Julian and standard date formats, this greatly reduces the possibility of errors and typos coming into the date or time.
Cheers,
-Paul