(**) There are three types of this route:
(A). «X28»-service, which is following along the route with all said stops. It serves everyday, at that on weekdays to/from "Bensonhurst" only.
(B). The first type of «X28» short-service. From Sea Gate on weekdays morning buses are following only to "East 23rd Street/Fifth Avenue", and toward Brooklyn on weekdays evening buses are following from this stop to "Sea Gate" or to "Bensonhurst". (No service north of 23rd Street in Manhattan; no weekend service.)
(C). The second type of «X28» short-service. On weekdays morning from "Bensonhurst" buses are following only to "Church Street/Thomas Street" stop; and begin evening weekdays "Bensonhurst"-bound service from "Broadway/Thomas Street". (No service north of Thomas Street in Manhattan and south of Canal Avenue in Brooklyn; no weekend service.)
PS: Also exists (D)-service, which was described on a separate page «X38».
On weekdays peak hours in the peak direction runs only (B) and (C) service; loop across Madison Avenue → East 57th Street → Fifth Avenue at this time served by «X38».
Full information you can see here