Random busses

Right... so i'm at the busstop where 3 busses come by... the 31, 36 and 328.... I'm waiting for bus 36..... the first bus that comes by.... 328.... and then 328.... 31....31...31...31... (yes 4 busses!!!)....328....328....31... YAY FINALLY A 36! .... 36 - not in service... BOLLOCKS!!!! half an hour later.... 36!!! yay!!! like DAMN! What happened with those busses?!