O que significa a drop in the ocean?

I have a friend who's been searching for a house these days. She considers renting one but everyone around her says the wise decision would be to buy it; paying for something that's going to be eventually hers. She doesn't know yet and is still figuring things out.

The thing is, when she talked to a real estate agent about the amount of money she'd need to make a down payment on the specific house she's interested in she realized she hasn't saved enough money to buy it just yet; that the money she's saved so far is just a drop in the ocean. Wait what?

"If something, especially an amount of money, is a drop in the ocean, it is very small in comparison with the amount which is needed or expected. This expression may come from a line in the Bible: `Behold, the nations are as a drop of a bucket, and are counted as the small dust of the balance.' (Isaiah 40:15)"

That's all for now guys. Take care.