When you move a gift to a new campaign, the amount of the gift will be removed from the original campaign and added to the totals of the new campaign. If the new campaign is completed, the totals may not update immediately, but a live campaign should update within 20 minutes.
Matches and challenges on both campaigns will not change from a move- any dollars the gift unlocked on the original campaign will remain unlocked and moving a gift to a new campaign will not active matches or challenges after being moved. Changes to matches and challenges must be done manually. We have a guide on editing matches and challenges here: Editing Offline Matches and Challenges