Here's my take on the scorecard mechanics:

Each line in 'scorecard' has a date field. The information on that line is 'as of' that date.

So, if you make an additional purchase on a different date, you should 'add as stock', duplicating the symbol, and enter the new purchase data on that line. When you save it, all lines for a given symbol will aggregate up into a summary line.

On the other hand, to adjust the original purchase data for any reason (wrong number of shares entered, wrong price entered, adjusting for a split, etc.), you should 'edit' the existing line, altering the quantity and price. BUT LEAVE THE DATE ALONE (unless THAT is what was wrong in the first place)! This will make the updated information reflect back to your original purchase date, which is what you want in this case:-)

If you SELL a stock, click on the 'sell' link and enter the date, number of shares sold and sale price. The scorecard will be updated accordingly, and a line will be created on the 'sold positions' tab reflecting the sale.

Use the 'delete' link if you want to obliterate all knowledge of transactions concerning the stock being deleted (but this will skew your 'returns' figures, by totally discounting activity in that stock).

Hope that is all clear.

HarryG