Reduce Quantity at 1st day of Booking disregard Duration

I’m working for a Tourism company.

The thing is,
we may have 3 similar tours but different starting date.

For instance, the dates are
1st of July , 2nd of July and 3rd of July.

Each tour can cope up to maximum of 40 quantity.

When I set Block duration to 3, and let say I booked on 1st of July.
All quantities of 2nd of July and 3rd of July was taken too while I hope they remain untouched.

Is there workaround for this? For workaround, the only way I know is to set Block duration to 1 and justify that as Starting date instead of displaying Tour duration.

Willing to buy Premium if there’s any solution.