Tstat7 Setup for Boiler and Buffer Tank

Head into the PID table, theres is where the output staging gets configured, number of heating and cooling stages get set and so on. The other examples for the Tstat8 will be a good guide.

Found a good example:

Tab7 shows the number of modes, two for your case: OFF and AUTO. You set them up correctly by the looks of it: In the AUTO table you have ON below setpooint and OFF above setpoint.
In the OFF table I assume everything will be off for both coasting and heating.