Why is my espresso flowing so fast [Breville barista touch]

Breville Barista Touch

Hi all,

Very much a beginner over here…having some troubles dialing in my machine. Currently using the Breville Barista Touch. Measuring out 18G of coffee, WDT, spring load tamp is my prep at the moment. Internal Burr of the machine set to the lowest it will go and external is at 23. Set to a 36 second brew time, espresso begins pulling around 7 second mark. It usually flows much too quickly and is yielding 70-90g of espresso in that time frame. When I grind the slightest bit finer, I get hardly any drops of espresso out. Continuing to experiment but not having the best of luck. Any advice would be greatly appreciated!