Your discussions of the future with yourself have given you peripheral knowledge about how events will play out. Whenever you finish a Short or Long Rest, the GM rolls a d20 and a d4 in secret and records the number rolled on the d20. The GM tells you the recorded d20 roll, unless they roll a 4 on the d4; in that case, they lie about the recorded d20 roll.
You can replace any D20 Test made by you or a creature you can see with the recorded d20 roll (no action required). You must choose to do so before the roll. If the GM lied about the roll, they inform you of the actual recorded d20 roll only after you replace the test with it.