I don't know what your brand is, but the "ひかぇめ" of oil heaters of Japanese brands generally means:

According to the room temperature, it will automatically turn off when it is higher than the set temperature by 3℃ and automatically ignite when it is lower than 1℃. Prevent overheating and supercooling. Which is what we call automatic mode.

If it helps, please adopt it. Thank you.