Each clock and data bit on disc is 2microseconds in duration which means a full byte is 32 microseconds (2 * 16 bits).
There is a specific bit pattern which is used for syncing. i.e. to ensure the data stream following it is always the same.
This special value is 4489. This is the pattern for clock and data, with a "missing clock" (in reality a single clock bit is forced to 0) and assumes that the data bit proceeding this has a value of 0 so that the first clock bit (bit 15) is 0. The data byte value of 4489 is 0x0a1. It is unique because the corresponding value computed from 0x0a1 has all the correct clocks and bits will not match this value.