Early evolution of the total mass, M_BH, bound (top panel), and number, N_BH, bound (middle), of the BHs and the number, N_NS, bound (bottom), of the NSs bound within the M_cl(0) = 5.0 × 10⁴ M_⊙ (initially all single stars) model cluster (see Sect. 3) for the various natal-kick engines (legends; see Sects. 3.1 and 3.2), for the F12-rapid+B16-PPSN/PSN remnant-mass model (Sect. 2.2; Z = 0.0001 is assumed). The collapse-asymmetry-driven kick engine produces relatively low kicks also for some NSs which marginally escape the cluster, taking time, resulting in their build-up at ≈20 Myr followed by a slow decline (bottom panel). After ≈55 Myr when the ECS-NSs begin to form, the latter’s population build up solely for all the kick-mechanism cases.