Calculate value for heater

Hello,
i did some first steps with home assistant and i’m realy happy with it.

But now i have an issue and don’t know how to solve it.

I think for you it’s not a big deal.

I’ve configured a numerical helper that stores the needed tempreture for my heating system.
Some of my rooms need an offset from this value.
So i created a new helper with the offset.

Now i want to calculate Value+Offset = new value

My actual configuration looks like this:

service: homematic.set_device_value
data:
  address: OEQ1715711
  param: SET_TEMPERATURE
  value: "{{ states('input_number.heiz_temperatur') }}"
  channel: 4

Can you give me hint how to get the value to the calculated value?

Thanks a lot
Alex