Did you check the notes? War mapper's data includes all territories since 2014, that's why the number doesn't match the White House. War mapper is showing what percentage Russia occupies including crimea and Donbas. The White House is talking about how much territory ukraine has taken back of the additional territory Russia has captured since February 2022, they exclude all territorial changes prior to February 2022
Before Feb22 Russia occupied 42k km2, then in 2022 they took a further 120k km2. White House says ukraine has taken back 50% of the 120k km2 = 60k km2. If you compare 60k km2 to the total land including from 2014 then ukraine has taken back 36%