In an onion root at metaphase in mitosis if there are seven chromosomes why should that worry me?

I'm not sure how many chromosomes an onion root has, however... during metaphase when the chromosomes line up, they have already under gone replication. This means there should be an even number of chromosomes. If you have an odd number of chromosomes, then either, one chromosome didn't replicate at all (most likely) or one chromosome replicated twice (less likely).