Attention to Detail

So, I'm in this critique group, right? And I've put my dystopian out there for them to read, and some questions have come up about the details.  The minute details.  Let me be specific because I want to know if these are actually issues I need to address, or if I can be a little vague about it.  

The majority of the population has been wiped out due to a virus.  How specific do I have to be?  Can I just leave it at that, or are people going to want an exact percentage?


The main character is...