Clearer instructions about confirmation press in the calculator practice screen

[jimmylogan]

The instruction for setting up alert on disguise screen (calculator) doesn’t include the need to press the same button again after vibration. It does get mentioned in a pop-up text during vibration and is lost quite quickly. It may be hard for some to read/understand (especially for those whom English is a second language).

We suggest that the pop-up stays up for longer or else that the need for confirmation is included in the initial invitation to try it now.

[jmatsushita]

As we implement the different configurations with #107 then we can finalise this.