Apparently, i made a mistake in the way i calculated the return for May 2012. Here's the corrected numbers...
APRIL 2012
Start Net Liqu : $20,000.00
End Net Liqu : $20,031.86
Net P&L : $31.86
Return : 0.16%
MAY 2012
Start Net Liqu : $20,031.86
End Net Liqu : $30,269.63
Deposit : $10,000.00
Net P&L : $237.77
Return : 3.11%
JUNE 2012
Start Net Liqu : $30,269.63
End Net Liqu : $31,749.50
Net P&L : $1,479.89
Return : 4.89%
Total P&L since inception of the account : $1,749.52
Total percentage return since inception of the account : 8.16%
note: i don't how IB came up with 2nd quater return of 8.34%...i find 8.16%..