Huck and Tom quickly decide they must free Jim from the Phelps's shed, but Tom is determined that the escape must be carried out with all the proper challenges and difficulties observed.
Obviously, the proper way for a prisoner to escape was to dig out of the prison cell, which Tom estimates usually takes thirty-seven years. Unfortunately, it would not be possible or practical for Tom and Huck to allow Jim to remain in the shed that long. Tom reluctantly comes up with an alternative plan for Jim's escape that will allow him to gain his freedom while allowing all of them to save their reputations, in spite of not doing it in the accepted manner and according to the accepted timeline.
What I recommend is this: that we really dig right in, as quick as we can; and after that, we can let on, to ourselves, that we was at it thirty-seven years.