("Tweetline" is a slightly obnoxious made-up word, but's let try to stomach it for now.)
Each tweetline is arranged according to the post time of each tweet. In other words, the tweetlines recreate the real time in which the story is being told.
It is also true that the tweets (and therefore the corresponding entries) are arranged in the order given by Baedeker's itineraries.
What they are NOT is representations of how long it took to move from location A to location B.