This might not be available at all Myers, as it was just a small sign in the Carindale store's toy section.

It gives you 20% off all toys until Sunday 9th, but only off the regular pricing. Any sale items that are cheaper, you get that price instead (it's the lesser of the two values).

For example, the FOC 2-packs are on sale until Dec 24th for $13, but the 20%-off price is $12 (so you get if for $12 for the next 5 days).
However, the FOC Voyagers are on sale for $40, which is the same as the 20%-off price, so it stays at the same sale price.
Everything else is 20%-off.

But unless it is reported in all stores, look for a notice at the store before expecting the discount.