Can someone please explain how using these numbers help in picking a table?
The site I play also has
Hands per hour
average pot size
% flop seen
And how long are these numbers tracked for normally?
Hi. Well a high % flop seen and a high average pot size means people are playing looser and are not afraid to get money in. That is usually a good thing for you. Depending on the site/stakes if the % flop seen is in the high twenties or above range that's usually a pretty loose table.
For the most part it's less enjoyable to play on tables with low % flop seen and low % average pot size as it's usually pretty nitty - passing blinds around. Though sometimes you can do OK on a nitty table stealing blinds and playing aggressively (sometimes not though).
Hands per hour is kind of a personal preference, some people cannot stand to play on slow tables. If slow action tilts you stay away, otherwise the other numbers are more important.