Your energy spend compares your last month's energy use with the previous month. When we move from summer into autumn, it's not unusual to see a big percentage increase in your energy spend – even if you're only using a little more energy.
As the weather gets colder and nights get shorter, we tend to turn on the heating and use more lighting. Because our energy spend is lower in summer, it can look like a big percentage increase month-on-month. Any percentage increase above 99% shows as >99%.