補論 is read as ほろん (horon) and means addendum.
ほろん
horon
ほじょ
spotting (in weight training)
ほきょう
reinforcement
ほせい
correction
ほきゅう
supply
ほけつ
filling a vacancy
ほそく
supplement
おぎなう
to supplement
ほせいよさん
revised budget
ほかん
complementation
おぎない
replenishment
ほしゅう
supplementary lessons
ほどう
guidance