i'm a new user and I'm a little lost ! Be patient with me please

so....
I played a while with the pratice mode, making good profit with smale stake.
AND I tried this strategy with horse's racing :
http://www.youtube.com/watch?v=sM5L2QnwbV4
In practice mode it works !
I used the "Trading profit calculator" or moving my ordre directly in the ladder to close my order
BUT

I reproduced exactly the same in real mode and....
When I close an order with positive P&L in Betangel : I'v got always EXACTLY a 0 EUR profit In my Betfair's P&L
For instance :
I layed the horse "Golden ticket" before the match at 8.00 with stake 2€
then the Trading profit calculator show me 8£ profit at 12.00
THEN I Close the order, they matched and on betfair I show + 8£
but on Betfair Profit & Loss I see :
Horse Racing > Belle 18th Aug : 2m4f Hcap Hrd Showing 1 - 2 of 2 Selections
Selection Odds Stake(€) Bid type Placed Profit/loss(€)
Golden Ticket 12.00 2.00 Back 18-Aug-11 18:12 -2.00
Golden Ticket 8.00 2.00 Lay 18-Aug-11 18:05 2.00
Net market total : 0
???? Where is my mistake ? Why I have this difference ??
please help me (and sorry for my bad english !!)
Regards
Stephane