Shoddy work not worth the cheap price. We ordered two pairs of glasses with an identical prescription. We received two pairs of glasses with slightly different prescriptions.
When worn, one pair would result in slightly blurred vision, dizziness, etc so we took them to an independent retailer and sure enough the axis on both lenses was off slightly (on the messed up pair).
We contacted customer support and sent the glasses back. After a month or so they came back to us (after we had to ask them what is going on) and said the glasses were fine. We asked about the difference in prescription and they said they would test them again.
Finally got back to us that the glasses were within an acceptable margin of error.
They have an acceptable "margin of error" when producing glasses to match a prescription.
In other words, what you order is not necessarily what you get - but that is just fine. You'll "get used to them."