If the correction results in you owing them money, you typically just need to pay them the appropriate amount. I believe they charge back-dated interest on the amount if it was supposed to have been paid in the past, but if it's for this year's taxes then payment isn't due until the end of April and so interest would not apply.
In some circumstances, they may apply fines or press charges for tax evasion, but only if they have reason to believe you intentionally/knowingly attempted to misrepresent your tax return in order to avoid paying taxes. You can challenge their decision to fine you, but you are considered guilty until proven innocent. Obviously that's the opposite for any criminal charges. The good news is, lots of people accidentally enter the wrong numbers and the CRA is aware of this and rarely takes action against them, other than making them pay what they owe. They have ways to look for suspicious behavior and differentiate that from innocent mistakes. So don't worry, you should be fine, not fined.