Thanks for your response.  This is the detail I have taken from the Print Label Section 

this section: indicates 10% rebate on items up to 500 grams.  see further below..one for cost of $7.20 the other $7.15 it would appear only the calculated post at $7.20 eg parcel post which can be up to 500 grams gets the rebate.

This is notice is actually not correct and misleading