No. They are two heaters in two different locations in your tank. Whilst its a good idea to have a couple sometimes, the temperature in different parts of the tank will differ slightly. It would be impossible to have them working in unison unless you have them both connected to a temperature probe. The temperature knob on each of them is not precise either. As long as your tank temp is within an acceptable range then there is no need to worry. If they are JUWEL heaters you will find they are often not very well calibrated and you have to set them higher than the temp you want to achieve.
