There was no mistake or misunderstanding. I highly doubt he even wrote the speech himself. All politicians lie, Ryan's were just extra-blatant this time and he was called out on them. Not that it really matters anyway. He told his base constituents what they wanted to hear. Most people don't actually want to hear the facts, they just want to cheer about something.
These are the times we live, unfortunately.
EDIT: I really shouldn't have said "Most people...blah blah", as last time I checked, I don't know most people. I'm just depressed at the current state of the government. Its been a sad couple of decades for anyone who is fiscally conservative and socially liberal. Having to choose the lesser of two evils every election for most of my life is tiresome. I actually had a lot of hope in Obama. Unfortunately, I am equally disappointed in his first term. I don't really understand why Republicans can hate the guy so much, since he really hasn't changed much at all.
I'm going to put myself in the line of fire and link a (albeit) crappy YouTube clip of Bill Maher. Try to not click it off after he takes a couple pot shots at Ted, he actually says some interesting stuff about how liberals feel about Obama's first term.
http://www.youtube.com/watch?v=pwq6_TyHMDg
His last line sums up my stance on Presidential elections: [Democrats:] Elect us, we're lame, but the other guys are nuts.