What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Deleting the submisisons with upload submission on them will do clear your account storage space used.
I checked your account/username curbd, and I can see that you are indeed on Overlimit Status already due to exceed limit in storage used.
This is because your jotform http://www.jotform.us/form/52948045116153 do still have existing submissions with uploads on them. You have not deleted them yet.
Please take cautions when deleting submission data because they are not recoverable once deleted.
Hope this help. Let us know if you need further assistance.