In the rules it says the large ball is to be introduced when there are 30 seconds left. Is that to be interpreted as ‘the ball must be placed when there are 30 seconds left’ or as ’ the ball may be placed at any time when there are less than 30 seconds left in the match’?
The VEX Clean Sweep Manual was recently updated to clarify this situation.
To answer your specific question, the large ball must be introduced at any time when there are less than 30 seconds left in the match.