Comment by ce4

It does make sense though (once you know where it comes from):

Before the ubiquity of watches, time was announced using church clocks and bell strikes. There's a big bell for hours (low pitch) and a smaller one for announcing quarters (higher pitch).

Signalling zero is not possible using "zero bell strikes", so 00:00 is signalled by 4 strikes of the quarters bell and 12 strikes of the hour bell.

Thus, the sequences go like:

11:15 1x quarter bell

11:30 2x quarter bell

11:45 3x quarter bell

12:00 4x quarter bell + 1x hour bell

Basically it makes sense then as all the quarters belong to the same hour.