Non-PRO English to French Marketing Business/Commerce (general)

Is the following sentence:
"Had I not personally declined the opportunity to join in, I am told, the answer would have been about 18 - the diet needs to continue!"

means something like:

"Bien que je n’ai personnellement pas décliné l’invitation, il paraîtrait qu’avec moi la réponse aurait été d’environ 18"

Context= a guess about how many people can fit in a xxx car

Thanks again