If the quantity on the label says 28 and there's not 28 pills in there originally, then pharmacy is at fault.
Not sure what you mean by "label doesn't match instructions on the same label"
Prescriptions go through several steps. First is often called "data entry" where someone looks at either the electronic/faxed/written copy of the prescription depending on how it was sent and types the information on it into the pharmacy's system to keep a record of it. This includes typing in the quantity, directions, day supply, prescriber, etc.
Then it goes through "drug utilization review" which means the licensed pharmacist looks at the prescription and makes sure that no errors have occurred during data entry in addition to making sure that there are no drug interactions or unlawful crap going on with the prescription. The reviewed, directions, quantity, prescriber, etc. is what goes on the label that is found on your bottle.
So if there are any errors that was done in step 1 that was failed to be caught by the pharmacist in step 2, it's the pharmacy's fault. But it's all about interpreting what the prescription says. If the pharmacist feels that there is any ambiguity, they would likely contact the prescriber for clarification.