What does the error Form over Quota Mean?

I have a user who got the attached error message. What does this mean?

This means that you have reached your submission limits for this month. 

Upon checking the account ncctraining, you have already reached the 100 regular submissions per month. Please check our pricing page here for the limits of each account type: http://www.jotform.com/pricing. If you reached any of the submission limits, your forms will temporarily be disabled, you'll need to upgrade to a higher subscription plan to continue using them, OR if you do not wish to purchase a paid subscription, you can wait for the submission limit counter to reset, this happens every 1st day of the month. 

Do let us know if you need more information on this.

Thank you.