Please keep track of your remaining time, if you exceed one hour you'll have to pay an extension fee.
Please keep checking your remaining time, if you exceed one hour it'll cost you and extension fee.
1) "1時間を過ぎると延長料金が発生しますので残り時間を確認してください" という意味です.
1時間を過ぎると : if you exceed one hour.
延長料金が発生します: you'll have to pay an extension fee / it'll cost you and extension fee.
残り時間を確認してください : please keep track of the remaining time / please keep checking the remaining time.