Our visa has an issue date of the interview date. We didn't have any 'under administration processing' issue. The date is 20th February, and it is valid until 19th August. In the embassy in Hungary, we were told before the interview, that if we want they can postpone the issuance of the visa (by how much time, it was not specified), if we want to, but we didn't take this option.
As as 44xxx said, you can request to postpone your interview date, which will push back your 6 month window for traveling. I did have to postpone our interview as well, just had to call the embassy, and they were quite flexible about it, they asked when we can go. This was the embassy in Hungary, which doesn't seem like a high traffic embassy from DV point of view, so your milage may vary on the flexibility, but it is an option.
Hope this helps.