The digits on your ticket must match the winning numbers at the corresponding position.
You'll get bonus if they match the digits in the correct order.
Here's an example lottery draw, with two tickets, A and B.
Ticket A: The ticket matches winning numbers at 4 positions, so the ticket wins 4 shares from the "Match at position" prize bracket. Additionally, the ticket matches winning numbers in the first 3 digits, so the ticket wins also "Match first 3" prize.
Ticket B: The ticket also matches winning numbers at 4 positions, so the ticket wins 4 shares from the "Match at position" prize bracket. But the first digit is wrong, so this ticket doesn't win any bonus prize.
The bonus prize brackets don't stack: if you match the first 3 digits in order, you'll only win bonus from the "Match first 3" bracket, and not from "Match first 1" and "Match first 2".