How does the scroll system work?

Sadly all that can really definitively prove is that you had fairly decent luck/results when doing those. Without being shown the formula they use to generate these numbers, any set of data values, no matter how many there are, cannot, beyond a reasonable doubt, prove anything. You can make assumptions as to if their system stays true to the claimed percentages or not, but that is about all you can do.

I had success rates closer to the normal 70% when scrolling normally though.