No earlier than 10 days before and no later than 3

English as a Second Language English Vocabulary, Grammar and Idioms
1

I got an email asking me to confirm my appointment saying a weird sentence.

"Congratulations, your booking was successful.
Y[color=red]ou need to confirm the booking no earlier than 10 days before and no later than 3 days before the appointment. Without that confirmation, the system will automatically cancel the booking.
Relatives applying together with businessmen can not be added automatically in appointment. They have to book a separate slot.
All of the necessary documents shall be brought in paper form and presented during the application. Any documents sent through e-mail will not be taken into consideration.
"

No earlier than 10 days means 11,12,13,… days before the appointment. In other words I can conform the date of appointment from today until 10 days before the appointment.

and

No later than 3 days means 2 or 1 day before the appointment.

I think they wanted to say 3 to 10 days prior to the appointment, but they made a mistake writing it.

Your comments would be highly appreciated.
Amir

2

Just the other way round. It means the countdown starts from that point—10 days before the appointment—and finishes with three days left.

3

How come?
Could you please explain?

4

Yes. But I don’t think they have made any mistake. Suppose your ten days span May 1 to May 10. The last three days are to be excepted. That means you have only seven days. So, you have to count back from the third day like this May 7, 6, 5, 4, 3, 2, 1 during which you have to confirm it.