Start point data was based on money supply and block reward as of yesterday, and the projections are based on the 0.5% block reward reduction every 10,080 blocks and the assumption that the smoothed, long term block discovery rate equals the current rate.

Good question. Thanks for asking. I thought it was evident, but by the looks of the lack of response, I think you were not alone in wondering. I've also edited the original to include that information.