Hi Mansour!
Apparently the journal or subscription is posted twice.
As invoice proposal comes from the posted journal Fee or Hours etc or the Service Subscriptions, it is producing double proposal.
In case of Journal, you have to fist Adjust transactions to void the first journal,
or simply post a journal of the same amount in negative -> make an invoice proposal with the same + and - amounts, --> Post it, Final invoice with 0 would not leave to the customer (in case of automatic invoicing).
In case of Service Subscription is run twice, delete one service subscription run from Service Management-->Service subscription-->subscription log.
Let me know further if this is any of help.