All the data of booked ticked they have it digitally on computer.
Based on it they manipulate the result.
They are using opaque white balls because they manipulate there weight. They might be having a chip inside each ball, or they manually add a weight before every draw for unwinning balls as they have the ticket data,
Each draw close at 10pm and result are drawn at 10.30pm They have the 30 minutes time, to make there draw prepared and add weight logic to numbers.
Solution 1
The Balls used should be in transparency glass color, So user can view through it. Draw should be drawn immediate at 10 pm only. No buffer time should be taken to manipulate result.
Solution 2
Or better approach a person to take the number from the draw manually by hand,