Since when is a month 28 days long?!

Since when is a month 28 days long?

In 15 years, I've had three prescriptions (not counting the pill). My doctor recommended that I take each one daily for a month.

So the chemist supplied me with 28 tablets?!
"It's the usual practice", or so they said. Is it?
I rang my doctor to check, and suddenly they added two other tablets to the packet, and told me
"We won't charge you for that".
This has now happened for the third time.

I certainly don't get paid every 28 days, and I think it's really rare to find a month that is 28 days long. Why should anyone pay for a month's supply and receive only 28 doses?
OK, why is this? Are they being cheap?
If the ideal is to take tablets for a month, how many days should that be? What do you all think?

4 weeks ago
I'd like to know if anyone here has had to take tablets for longer than a month, and has noticed this too? It seems a bit cheeky to me.

Yes this is normal in medicine as the human body goes through its cycles by a 28 day cycle - hormones, blood everything!