Reducing can be seen as lessening and this happens when in anaphase 1 of meiosis the chromosome sets are isolated (a dividing = decrease).
While reaarangement can be simply imagined as a revamp of chromosomes happens in metaphase 1 of meiosis when the chromosome sets line up on the equator freely of each other - eg in people with 23 chromosome matches there are 2 raised to the power of 23 manners by which the chromosome sets can adjust = more noteworthy than 8,000,000 mixes.