Scale value in HTTP output for target temperature setting Rademacher thermostat

My Rademacher thermostat handles the value for temperature in deci degree:

value 200 = 20°C

I was able to transform the input value with JS transformation:

(function(i) {
var o = JSON.parse(i);
var temp = o.device.position;
return(temp * 0.1);

But how do I transform the output? I have to multiply the target temp with 10, but transformations are not possible with GET outputs (only with POST).

Thanks a lot for your help!!