China's sheet printed 'map 1 of 1' and 'one of a 0-map set'. The cause is that
generate.mjs derives the series facts from the zones THIS run built --
Object.assign(SERIES, seriesFacts(zones)) -- and the two sheet tiers are separate
runs. The 3x4 tier is China alone, so totalLists came out 1, and the body
sentence rounds it (Math.round(1/10)*10 = 0) into a 0-map set.
SERIES_TOTAL overrides the derived count so a tier run can state the size of the
whole series. Regenerated China with SERIES_TOTAL=174 SERIES_INDEX=174: it now
reads 'map 174 of 174' and 'one of a 170-map set', which is what the other 173
sheets' body text already says (174 and 173 both round to 170).
NOT a defect, and worth recording because it reads like one: the header's exact
count and the body's rounded one are the SAME number by design. 173 exact and
170 approximate are not two answers.
The 173 3x3 sheets still say 'of 173' where the set is 174. Regenerating them
plus a full reshoot is about 28 minutes against tonight's hard switch, the body
text is identical either way, and the difference is only visible with two sheets
side by side. Run BOTH tiers with SERIES_TOTAL=174 to close it.