There are a couple of more pointers to indicate dispensing with any mystery, Rebecca. The word "cannot", indicates doubt rather than a statement, ie, "
you cannot be more than twenty? ", (as opposed to "are-not") is a guess question rather than a fact. There is also no reason for Jane Austen to leave anything unexplained in a story where everything is neatly tidied away even to telling us the aftermath. The Bennets are not the type of people to be involved in any deep secrets and again, Jane Austen never gave any hint of such. There are many things in the story to puzzle about, such as Bingley's history. Darcy claimed to Lizzy that Bingley had many friends, where they also Darcy's friends? During the story the pair seem to spend a fair amount of time together, but are such diverse characters that even that seems strange. Where are all the friends? Are they in London or back in the north? Bingley is said to have not long reached coming of age ( if common consensus is to be believed). To marry, both male and female required parental consent before the age of twenty one. It's all a mater for persoanl specualtion.
I agree with Rae Elaine's views on grammar and printing errors occuring and escaping editing notice, that happens even today.
