What's Wrong with People? Don't They Know How to Read?

I'm finally back to my section after covering my colleagues for the past week. Things were going fine, until this patient from an elite school (he was wearing his sch uniform) asked me if he needed to take a queue number to collect his medication. Some may think this is just a harmless question, and I probably should not be making such a big fuss.

Problem is there is a clear signage at the counter instructing patients to :
1. Press the green button for 2 queue tickets
2. Attach one of the queue tickets to the prescription, while the other ticket is to be retained by the patient.
3. Leave the prescription in the tray for processing (the tray's attached to the signage).

It really bugs me that everyday there will be patients asking the same question, and we're not talking about the poorly educated patients. Civil servants, army personnels, students from elite schools... What is wrong with them?! Can't they read?! Else they can follow steps 1 & 2, but experience brain freeze with step 3; they walk off with the prescription instead of leaving it in the tray for the staff to process. These people... they're just contributing to my frustrations.

Just testing... I know some like to start things off with a bang, but I take time to warm up so this is just a simple message to start off.