[JamesMowery]

I don't definitively know the answer to this, but my thinking here is that it could be related to your next year's available budget for player contracts (since your players could theoretically have higher contract values for the next year). If you have a look at your salaries for upcoming seasons, there might be a correlation to this.

Just a thought. Hopefully someone else can confirm that this is reason, as I'm curious myself.

Edit: I just fired up the game and had a quick look, and I'm not so sure that my theory holds true. Perhaps someone else has an explanation?

Edit 2: I did some more math, and I got it: Take your Next Year predicted BUDGET and subtract it by the next year's total EXPENSES SUBTOTAL (you can see this in the "Accounting" tab under your Front Office). The remainder is your available amount for extensions.

Edit 3: I'm an idiot. There's already an "Extension Information" section in the Front Office Financials section. It's past 1 AM and I'm tired. :P