Yes, those sort of figures are disconcerting when you first hear it, isn't it - though I've heard worse from other agents.
But you do have to remember that well over 50% of the 4000 or whatever their figure was, are total no-hopers. As the immortal Slushkiller post says, if your book has "a sufficiently functional plot that readers would notice if you shuffled the chapters into a new order", then you're in the top 50% or so.
And if it's of a quality that makes them think "someone could publish this book " but not them, then you're somewhere in the top 1-5% of that 4,000
http://nielsenhayden.com/makinglight/archives/004641.html