Cgracek, welcome to Bluelight. Your new so I just want to make you aware that this is not typical material for Other Drugs. The forum itself is centered around Harm Reduction, which means just what it sounds like. Attempting to ensure that recreational substance users can do their thing but still maintain a certain level of personal safety. There are other forums on Bluelight that are less serious where you can post questions like this. I suggest you read the rules and explore the site to get a better feel for it, but I will attempt a response to your query.
With almost all of my prescriptions it's normal to receive my new prescription 2 days early. I've never asked, but common sense tells me that this is done to ensure the the patient does not run out of medication as things happen - couldn't make it to the pharmacy, car broke down etc. I take a C5 medication and I typically receive my prescription at the 28 day mark and believe me, I pick it up as soon as I get the e-mail from Walgreens. However, an amphetamine prescription is significantly more controlled, so I am admittedly unaware of just how strict the refill schedule is. Pharmacies do make mistakes; it is definitely rare, but it does happen.
You could always ask the pharmacist. It's an innocent enough question really. "Hi, I would just like to know what date I will be picking up my next refill as I really like to plan ahead on these things." That will solve your problem. Good luck.