Orin's first call: the day that starts before 0600
Because he left his dormitory room before 0600 for dawn drills and often didn’t get back there until after supper, packing his book bag and knapsack and gear bag for the whole day, together with selecting his best-strung racquets—it all took Hal some time.
Context
The regimen's daily shape, given as pure logistics: out "before 0600 for dawn drills" and not back "until after supper," so the whole day has to be packed in the dark at once — books, gear, "his best-strung racquets." The athletic body's schedule swallows the day end to end; there's no returning to the room, so the body carries everything it will need for its many functions from before dawn. "Selecting his best-strung racquets" is the tell — even the packing is a conditioning decision, the instruments chosen by string-tension before the sun's up.