Graphs showing TWh lower than MWh

[VT-UKPN]

[slowe]

The logic in the formatting code was wrong. The input data is "kWh" so it now uses the following logical checks:

• ≥1e9 → divides by 1e9 and uses "PWh" (petawatt hours)
• < 1e9 and ≥1e6 → divides by 1e6 and uses "TWh" (terawatt hours)
• <1e6 and ≥1e3 → divides by 1e3 and uses "MWh" (megawatt hours)