That's a rather misleading statistic. Some is absorbed by oceans, where it acidifies. For land based carbon sinks (trees, soil, etc) any new carbon being deposited is competing with existing carbon in the carbon cycle.

If your stat had any sense then atmospheric carbon levels would rapidly plunge in a few centuries without humans burning carbon. They plainly don't do that.

Carbon levels are expected to plunge over a few centuries if carbon emissions drop.

You are right the the ocean is the largest carbon sink, and it has the negative side effect of acidifying.