Notes. Initially the ice giant (IG18) has 1100×500=5.5 × 10⁵ moons in the inner moon region; after its encounter with Neptune (encounter distances shown in Col. 1), a fraction are lost from the IG (Col.2). Some are captured by Neptune (Col. 3). Going into the detailed classification, a fraction can be orbitally circularised in 4 Gyr, also not disrupting Nereid, referred to as circularisable moons (CM). However, some of the CMs may be lost to Neptune due to tidal drift; those not absorbed by Neptune are called survivable CMs (SCMs). Moons on retrograde (R) orbits usually driftinwards faster and are thus more likely to be engulfed than those prograde (P). Hence, the fraction of SCMs (P), where we assume all moons are prograde, is larger than that of SCMs (R). Uncircularisable moons, if on orbits wider than 70 R_Nep, are classified as irregular moons (IMs). We have two models for orbital circularisation: tides only and collisions+tides. So we list the fractions of CMs, SCMs (P), SCMs (R), and IMs for the tides-only model in Cols. 4–7, and those for the collisions+tides model in Cols. 8 to 11. All fractions are the number of each type of moons divided by the initial total number at IG18, 5.5 × 10⁵. See Fig. 2 for the orbits of each type of moon.