The reversal of the two decrees is all within Allah's knowledge and is recorded in the Preserved Tablet. The person himself knows nothing of his own destiny or of Allah's decrees, but what he does know is that if he performs certain good deeds, then He will increase his profit (as in the example above) more than if he does not do that deed.
The reversal of the two decrees is known to Allah and is documented in the Preserved Tablet. The individual has no knowledge of their own destiny or Allah's decrees, but they understand that performing good deeds will increase their reward (as illustrated by the example above) more than not doing them.