Please forgive this lateness, I ought to have posted this sooner.
I looked to see what measure an amos is and I found the measurement of 18 inches with a GOOGLE search. But this didn't make sense to me in the contect of this daf material:
"in a bathhouse;
(o) Answer (Beraisa): If one ate and did not walk "four Amos" before going to sleep (Rambam - if one did not walk "four Amos" [or exert himself in another way] before eating), the food [will not be digested properly, it] will rot [inside him] - this will lead to bad breath..."
I'm not clear why it does not make sense. The Beraisa recommends walking a minimum of four Amos, or approximately 6 feet, in order to stimulate the digestive muscles. One who lies down immediately after eating (as might have been common in the days when people ate while reclining on low beds, cushions, or couches, with small individual tables in front of them) will be prone to digestive problems.