how many guests did you have to guarantee???

I'm booked for the Bourne Mansion on a SAturday night and I don't remember if I 'had' to guarantee 175 for the night or if we just volunteered that number because I thought we were going to be around 200. Now I'm beating myself up because we're only going to be 150 and I'm thinking I'm going to be paying for 15 plates for no reason. Once you have a guaranteed minimum and it's in the contract, there's really no more negotiating, right? I just hate to pay an extra $2500 for no reason. I just never expected that so many people wouldn't be able to come. Are there any other Bourne brides out there who know that we actually do 'have to' guarantee a certain amount for a Saturday night so I don't beat myself up anymore????
I'm curious to hear what other brides had to guarantee.................