There is no need to do so AFTER adding the two part, but BEFORE you add it.
- you need to measure before as this defines you how much 2 part you have too add
- It is absolutely clear how much Ca / Alk is added by the 2 part based on the recipe
If you want to measure anyhow and check the 2 part, your system should have „mixed in“ the 2 part which is done normally in about 5 minutes.