Bigger number is a bigger bike. In that bike, 24 is
large...the largest size they make. A 5' 10" person is of about average height, and probably should use a medium-sized bike...that would be about a 19 in that bike. That's not an absolute, but it's the place you should start looking for a fit.
From the Specialized website: Size 12 15 17 19 21 24
http://www.specialized.com/bc/SBCGeo...76&language=US
You might start by reading what Sheldon Brown had to say about the subject of bike sizes:
http://www.sheldonbrown.com/frame-sizing.html