When any channel is used in the formula, it is memorized by its index. But in certain cases it is useful that the channel is memorized by its name.
For example, we use a sensor with TEDS which has a pre-defined name "Sensor" on the first analog input. This channel gets index 1;0 by default. We want to use this channel in Formula math for additional calculations.
However, if in the next measurement the sensor can not be connected to the same input, but instead is connected to another input, the channel gets a different index. Consequently, the previously created formula will not make the correct calculation since the cannel was only remembered by its index.
If we want the formula to remember the name of the channel, an additional "@" sign must be added in front of the channel name.