There is no dedicated instruction available in Twido Suite to calculate totalized value, You will have to write your own instruction.
Please find the sample application where I have create Totalizer using simple instruction. In this sample you will just have input flow value as analog input. Then you will have to select the unit of flow rate of analog input signal as Second for unit/second, minute for unit/minute and hour for unit/hour. Then after you will have to press start button to start the totalizer.
You will get the result output in float variable %MF6.
Using this application no matter how frequently you collect the sample of flow it will be integrated into totalizer basis on unit of measured value.