Did they issue you multiple $50 vouchers like the other person said? I fly mostly from SFO to HND (Japan) and it would be worthless if I only got $50 off a flight.
I've gotten several thousand dollars in vouchers over the years. I've never ever had gotten one which couldn't be stacked with other vouchers to pay for a flight.
Always an electronic voucher with the full amount offered. My last one was a 600$ voucher and I paid a full round trip to Europe with it.