"Seventy times seven" in Matthew 18:22 isn't a literal limit to forgiveness. The specific numbers are irrelevant. The point is that we shouldn't keep track of offenses. 10,000 talents in v24 was meant to convey the sense of an unpayable debt, a debtor without hope.

The debt we owe God is unpayable, beyond human comprehension, yet He forgives those who plead His mercy. There is nothing anyone can owe you that remotely compares to what God has forgiven you. If we're unwilling to forgive our brother a pittance, why should God forgive us a fortune?
See Matthew 18:22-35.