You are right, I don't know for sure that it's Marianna. I think because they were the only Matej/Matous couple in Hrotovice in the right time period, I theorize it could be Marianna. Oh, to be so lucky for it to be Justina, Magdalena, or something equally distinctive.
As for the accuracy, I've never really run into the dates being that off. Ages, yes. My great great grandfather appeared to be age 40 when he died, but the numbers appear to be off by 10 years. I'll have to look up the records now that they are online and check. As of now, I haven't published his death death on my website because it seems incorrect. So even though Andreas might not have been 78 when he died, that age makes him 26 when he was married, which is reasonable. Or he could have been 24 or 22. I looked that far forward. Or 36, as you say.
A couple of interesting things: 1) After having various Coufal children in the Krhov book in multiple villages, all of a sudden we go for about 15 years without any. I supposed the cousins could have all gotten to the stage where they had houses with teen-agers. But I really expected to see the next generation of children. I'll have to go to the next book. My math might be off by 4 years. :)
The second odd thing: in one of the posts with Kamil Holena, or else an off-line e-mail, we found a record which seemed to be a Coufal, house address and grandparents all matched, but with the last name of Knap. Kamil thought it was an error. I did find an Ondrej/Matej record with the last name of Knap close to the time frame in the Krhov book, a little earlier than expected. The thought occurred to me, to wonder if there were variations on surnames, like the French Canadians with their "dit". That's another post for another day, however.