Access request to feeGrowthOutside specs notion page

[junomonster]

https://github.com/perpetual-protocol/perp-curie-contract/blob/f98ff086f4147680d579f68db7f3baedd6fc0063/contracts/lib/Tick.sol#L70-L79

We're currently doing some uniswap v3/trident stuffs, accidentally we found some articles about the uniswap's underflow issue.

According to this (https://github.com/Uniswap/v3-periphery/issues/164), I assume that this is why perpetual team does not use safemath on the fee growth calculation logic.

However, I cannot understand that how the under/overflow situation occurs. To resolve this, I wanna get an access to that notion page.

Thanks.