Could anyone please help me to rectify the following problem.

Compounded Half-yearly ie 2
ROI 8% (=8%/2) ie 0.04
Term(Yrs) 6
Term (Months) 0
TotTerm 6 (=6*2) ie 12
Instalment 1000 (=1000/2) ie 500


If I use Excel FV Function like this
FV(0.04, 12, -500, 0, 1)

The result becomes 7813.42

But if I calculate in the following way:

1000 6 =ROUND(1000*(1+(0.04))^(12),0) = 1601
1000 5 =ROUND(1000*(1+(0.04))^(10),0) = 1480
1000 4 =ROUND(1000*(1+(0.04))^(8),0) = 1369
1000 3 =ROUND(1000*(1+(0.04))^(6),0) = 1265
1000 2 =ROUND(1000*(1+(0.04))^(4),0) = 1170
1000 1 =ROUND(1000*(1+(0.04))^(2),0) = 1082

The result becomes 7967

The difference is being 153.58

I would like to know the correct Excel Function.

Regards,