Magento Data Revenue Doesnt Match Up

Hi does anyone know how Magento advanced reporting works out the revenue on the advanced analytics reports? their results is very different to what I have. I have tried to calculate net and gross revenue via the data which comes from report > sales> orders and show actual values.

when comparing revenue between advanced analytics revenue and my exported revenue, there is a fair difference in results between the two. advanced reporting, says 428660.73 in the passt 30 days, whereas my exported revenue from reports > sales > orders is roughly 20,000 higher.

I believe its due to revenue being calculated as net on the advanced reporting but when i try to find deductible items(refund, shipping, discount), i am still not that close to the advanced reporting figures.

any ideas or suggestions will be greatly appreciated. still extremely new to this and struggling big time with this platform