This amendment provides that if clause 262 of the bill, which is on page 153 and provides for the maximum partisan advertising expenses for a political party during the pre-election period, were to come into force after June 30, 2019, then it wouldn't apply to the pre-election period, which means that there would not be any maximum partisan advertising expenses for political parties during the pre-election period preceding the 2019 election.
On October 18th, 2018. See this statement in context.