The network fee is calculated based on the rate provided by Etherscan.
(For reference: https://etherscan.io/gastracker)
In addition, here is how the minimum withdrawable value for Social Good is calculated:
The minimum withdrawable value that the user can input = Minimal withdrawal amount decided by the Social Good Foundation OR (Network Fee + $0.01), whichever is bigger will be used.
*To find out more about the minimum withdrawal amount please see this article: How much "Approved SG" do I need in order to be able to withdraw my SG?