Viva Skylo flush valve - which number means more flush?

[RobertBrown84]

I have a Viva Skylo flush valve and want to adjust it for maximum flushing power on the full flush. None of the instructions indicate whether a higher or lower number will achieve this, and I can't see an obvious difference in the water volume. Anyone know how the adjustment works?

https://www.vivasanitary.co.uk/media/41178/SKY005.pdf