Incorrect stats?

[FlyingPenguin]

I wanted to do some calculations on rocket trajectories and used some stats provided in the building menu, in particularly the fuel consumption rate (FCR) on the total amount of fuel. I originally assumed that the displayed stats correspond to

internal values used by the game, however taking a look at the RT-10 Solid Fuel Booster engine shows that somethings seems to be slightly off. The engine has a total amount total of amount fuel units TF = 433.0. The fuel consumption rate reads FCR = 15.0864/s. Sow the burn time (BT) of the solid fuel engine is just given by BT = TF/FCR = (433.0/15.0864)*s = 28.70 s. However when I measured the actual burn time it was rather something like ~30s. So in total a deviation of 1.3 seconds. This is more than four times of my personal reaction times, so I'm really guessing the stats displayed in the menus are either incorrect or wrongly interpreted by me. Can anyone shine a light on this?

[Streetwind]

Numbers shown in the stats are the maximum possible volume flow rate. This means they are given for the lowest Isp value in the curve, usually the one found at sea level. If you launch a solid booster, it's going to gain height and thus gain Isp, becoming more fuel efficient and reducing the flow rate. Thus it burns slightly longer than you expect it to. If you hold the booster in place at sea level for its entire burn time it should be much closer to what you calculated.

(In real life, the fuel flow rate is always constant, and thrust output changes with Isp instead. In KSP, this was implemented differently because it makes building your rocket easier.)