I checked out that link and it has 31,250 as an actual baud rate with reload of FFh w/12MHz xtal... I don't really know what you mean (?)

If you use the baud rate calculator here at 8052 also, you get reload of FFh for exactly 31,250 baud.

TH1 = 256 - ((120000 / 384) / 31250) = 255

Thanks
John