Here the "current gross yield" maintained on the rental unit is displayed as "old value" and the "break-even gross yield" as "new value".
In the example, the current gross yield amounts to 7 %, the break-even gross yield 9 %. This results in a potential rent of (current rent * 9% / 7%) = 1285.71 SFR and a reserve of:
Potential rent - Current rent = 285.71 SFR
The percentage reserve is displayed here based not on the current rent but on the potential rent.