Moonrise is over land; moonset is over the sea
Mumbai faces the Arabian Sea to the west. The Moon always rises in the eastern half of the sky, so from the city reference it comes up over the eastern suburbs and the Thane creek side, not over the sea. The open sea horizon matters for moonset, which happens in the western half of the sky. Buildings near you decide when the Moon first becomes visible; this calculation assumes a flat horizon.
Source: GeoNames — Mumbai