Counting grain is one of question which mainly used to teach the concept of units digit, tens digit and hundreds digit (currently not supporting thousands digit). According to your question, you can set its answer, the size of counting grains and the total counting grains dragged by students.
Create a question in Editing mode
Enter the answer directly in the "Answer" column of properties panel.
How to use by students?
Students can drag the unit digit, tens digit and hundreds digit grains on the right hand side to the left box correspondingly. Same type of grains will automatically pasted together when student moves it closer to each other.
For example, student can move 10 unit digit grains to the left one by one, then they will pasted together as an object automatically. To untie these stick-ups, you can select the pasted grains and press the "Dissolve" button in the bottom right corner. To delete grains, you can select those grains and press the "Garbage" button in the bottom right corner.
P.S. After 10 unit digit grains pasted together, they cannot move to the tens digit box automatically but you can manually do so. Transformation of tens digit grains to the hundreds is the same.
However, if you shift one tens digit grain bar to the unit, they will be automatically disassembled. Transformation of hundreds digit grains to tens is the same.