When you add more ROOT to your current Nominated stake, it takes two Eras (Era = 24hr) to process, meaning that in the third Era, after adding to your current staked amount, you will see it reflected in your Active and earning amount.
Rewards for this stake increase will be calculated from the point the additional ROOT is added onward, it does not apply to any previous Eras in the current staking cycle.
Current Era: the task is queued to be broadcast to the Pallet during the rollover to the next Era.
2nd Era: the task is broadcast to the Pallet to Nominate the additional ROOT to your selected Validators.
3rd Era: the task is processed during the rollover to the next Era, and your Active and earning amount will reflect your full Nominated stake. It's important to note that rewards will increase proportionally from this activation point and will not apply retroactively to the prior Eras.