How to prevent issues when same slot is booked within Inventory widget?

I made a survey for my students. They can choose between three different projects. Each project has 20 places, so it is limited. The students might choose their projects as soon as I provide them the link of the survey. I tested my survey and found out that there is a problem. For example 19 places are already used and the last place is still available. Two students see that there is one place left and want to choose it. They do their choice each on an own device. So the press the submit-button around the same time. The system knows which student was quicker and got the place. But both students get the message that their submission has been received. But the students who was a little bit late does not know that his choice does not count (the system knows but he does not know it because he got a message that his submission has been received). How can I solve this problem?
Thank you for your help.

I'm afraid, we do not have an option to prevent issues like you described. But, as a confirmation, you can include the number of places booked in Thank You message and advise users to check it after submission. This way users will see if their submission has not included any place. Same can be done for email autoresponder.

Hope this helps! But, please get back to us if you need further assistance.