Please explain this!

If someone would be kind enough to explain to me how the ballpark thing at the bottom f the card works when you 're supposed to see how a card would perform in different stadiums. I don't understand it at all, or how to use it ... PLEASE HELP!!!

Changes in the colored bars at the bottom of the card will show the ballpark effects.

(The cards are being a little buggy - sometimes when I open a card the bars aren't there. I close the card and open another and then when i go back to the original card the bar is usually back).