The 'All time' metric at the top of your portfolio screen reflects the net result on your entire account. This figure therefore may go down a bit depending on the fees you have paid.
The formula is: Account Value - (deposits - withdrawals) - (cost basis portfolio transfer in - cost basis portfolio transfer out)
The ‘all time’ metric on iOS. (Android looks slightly different)
The 'Today' metric is calculated as follows:
Account Value Yesterday - Account Value Now - (deposits - withdrawals - chargebacks)