Parallel Operations Wrong Scheluding Times

Hi PP Gurus

Hope you can help me out to figure out next issue:

I have this routing

Std. Sequence | Parallel Sequence

Op.10

Op.20 - WC 1 | Op. 20 - WC 2

Op.30

Op.40

Say the avaliable capacity for WC 1 and WC 2 is 100 units per hour in each one.

When making a PO of 1000 units I hope to see the total process time in Op. 20 of 5 hours because I have 2 work centers assigned to this operation. But isted of having this time reduced I the total time for operations 20 is 10 hours.

Can any one help me out to figure out this issue??

Thanks all

Elias