When you order a new card you choose a start date for your megarider, but the start dates it shows take into account the delay in getting your card in the post.
If you already use a card you can choose a start date, but these dates take in to account the 3 days it could take to load your ticket on the card.
The T&C's on the leaflet say up to 3 working days to load your sale ticket onto a current card and up to 5 working days to reach you in the post if its a new card.