You said "产生的每个病毒全都出现了变异".

Genomic mutation rate is the average number of mutations per genome per replication. In my understanding, genomic mutation rate 1 means, ON AVERAGE, in every one thousand replications of genome, there are one thousand bases got replaced. But that does not translate into "产生的每个病毒全都出现了变异". Some "产生的病毒" have more than one bases got replaced, some have none. Yush's calculation still applies.