Speed Index Calculation help

[Redsauce]

I just picked up the Graphical Player 2008 and I’m taking a look at the speed index for batters. Problem is, I’m a little slow and I don’t understand it.
The description about the speed index says “Speed Index(SX) is just an estimate of the rate at which a hitter tries to steal (successfully or not).” It’s supposed to be a reflection of the manager’s tendency to send a player. The numbers in the book range from zero to 600, with lines at 200 & 400.
Can someone explain this in a way I can understand this? For the life of me I just can’t figure out what the Speed Index means or how it’s calculated. Thanks in advance!

[skyking162]

My guess (stress, GUESS) is that it's the percentage of times a runner is on first with second base open that he tries to steal. 600 might be .600 or 60%...

[Redsauce]

I thought about that too. Reason I don't think that's it is because of the 200/400/600 breakdown. It would make more sense to me if they made it a percentage (1-100) on the sidebar. But thank you for the input! This is still bugging the crap out of me. Next step, I guess, is emailing the book publishers.

[skyking162]

The scale might be each player's attempt rate divided by league average. Sounds reasonable that the speediest players try to steal 5-6 times as often as average. Zero is the minimum for that scale.

[Redsauce]

That might be it too. I guess I thought it was something really easy & obvious that I was missing. The other side of the graph for batters shows what they call PX which, in actuality, is just isolate slugging percentage. That's easy & simple, so I figured their speed index would be too. Now that I see it's not (at least as far as I can tell), it's frustrating that their explanation of a graph they use for every single batter in the book is so poor & unhelpful.
Thanks for the help, Skyking!
If anyone else has an inkling what's going on here, please post!

[pizzacutter]

I haven't seen the book, but I would guess that it's normed to the manager's tendencies. For example, if a manager sends the runners on the team in 10% of the situations involving a possible steal, but sends you only 5% of the time, he's probably trying to tell you something.

This would be helpful in splitting apart which players have SB totals because they play for teams that like to run and those who are just honestly good base stealers.