Not a lot of margin for error there—and again, remember that that's with a brand-new aircraft, perfect technique. With the somewhat clapped-out aerial conveyances given to most of us to fly, that may translate in real terms to 0 fpm.
If you're flying a clapped out aircraft, and suspect the performance is compromised, you should land it, and snag the defect, so that the required performance is accomplished.
The prevailing design requirement states in respect of the foregoing (with my bold):
Sec. 23.45
General.
(a) Unless otherwise prescribed, the performance requirements of this part must be met for--
(b) Performance data must be determined over not less than the following ranges of conditions--
(c) Performance data must be determined with the cowl flaps or other means for controlling the engine cooling air supply in the position used in the cooling tests required by Sec. 23.1041 to Sec. 23.1047.
(d) The available propulsive thrust must correspond to engine power, not exceeding the approved power, less--
(e) The performance, as affected by engine power or thrust, must be based on a relative humidity:
(f) Unless otherwise prescribed, in determining the takeoff and landing distances, changes in the airplane's configuration, speed, and power must be made in accordance with procedures established by the applicant for operation in service.
These procedures must be able to be executed consistently by pilots of average skill in atmospheric conditions reasonably expected to be encountered in service. (g) The following, as applicable, must be determined on a smooth, dry, hard-surfaced runway--
........
Amdt. 23-62, Eff. 1/31/2012