So it looks like the chart is actually meant to be a repair/maintenance chart—including, of course, minor maintenance. Of course, the whole context of this episode's beginning reinforces what Timothy says to Kirk in the Officer's Club: "I understand you're laying over for repairs," rather than "I understand you're laying over for completion of upgrades."
For various reasons I mentioned before, there's sufficient reason to doubt that the final chart in the episode (opposite to intentions of the script, e.g. "ships incoming") is a repair/maintenance chart.
Of course, the Enterprise is at Starbase 11 to repair the ion storm damage which pulls the ship from active duty for several days.
Now, a look at the starship status chart and in particular NCC-1701, could tell Stone that in addition
to the damage repair at Starbase 11 the Enterprise
is still in line to receive upgrades (13%) which will pull the ship again from active duty some time in the future.
Obviously, at some point in TOS, the ship must have spent three weeks at a shipyard to reboot the entire computer system to fix the computer's voice according to "Tomorrow Is Yesterday".
Of course I don't know how much idle time is acceptable for a 23rd Century Starship, but Stone's decision in "Court Martial" to put the Enterprise on priority one repair service, could simply be his contribution to help to keep the idle time at a minimum (seeing
that the ship will
spent more time in a shipyard, soon).