I am using the method suggested by the manual, more or less, or at least that is my primary reference, except I am not very active in updating it.

I don't know what the "key" is. If I were trying to figure it out, I would compare my trades with the trades from an underporfming account to see if there are any discrepancies. I would try to understand those first. From comparing trades I am assuming any major differences in terms of brokerage, slippage, spreads, swaps etc will come to light in reviewing the trades.