Doordash, How Do People Get $15 off Referral?

I have seen a lot of people that have $15 off referral in their referral link while all the other majority of the users have $5 off in the ref link.

How do these user manage to do this? For example there is like 400 referral links that have $15 off referral, is there any way I could make my account get from $5 to $15? Or make a new account? https://www.ozbargain.com.au/deals/doordash.com