Well, to me it seems that Bobba was chasing Solo and reported to the SD the direction he was going (to which planet he was probably going based on his course). Maybe Vader decided to get there first to set up the trap and said to Bobba to keep chasing Solo (in order to be sure he wouldn't change direction and get lost from the empire). In that scenario, the Empire got there first and Bobba got there in the same time as Solo.