The source explicitly distinguishes magnification, which concerns dignity and rank, from multiplicity, which concerns numerical abundance, magnitude, or extent.
PurposeMain focusIllustrative idea
MagnificationRank, eminence, grandeurAn exceptionally powerful protection
MultiplicityNumber or magnitudeNumerous camels or a large stock
DiminutionSmall extent or slight amountA very small portion
One thing may be unparalleled in importance without being many. Conversely, possessing many things does not make those things intrinsically noble. The two rhetorical aims require different explanations.