I do not quite understand how these markers work. Do the macedonian units in the harbours just wait doing nothing until the markers are removed? Do the tyrians also inflict hits on the markers until they are removed- or are tyrian hits taken on the "sitting duck" macedonians?
I am not sure but I guess the Macedonian player rolls each turn on column 4 until it accumulates 5 and 4 hits (Sidonian and Egyptian). Then the stack of Macedonian units is placed in the harbour square and normal play starts for them.
I think it simulates a siege procedure sgainst the harbours while Alexander is assaulting the Temple of Melkart.