There are a total of 151 systems, 305 dockable stations counting the CF docks double part (not sure if that happens somewhere else too, but I doubt so) and 237 confirmed jumpholes. Some players already have all the 237 jumpholes explored. There are few more stations "existing", but not dockable in Multiplayer, and some are not dockable at all for being unfinished or ment as support for some Singleplayer scripts.