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.
You can see your storage under your account:
Unfortunately, there is no easy way to see which form is taking your upload space, but the way you have explained above is the correct way to do it.
Basically you need to go into your submissions and delete the ones that are taking the space and this is only needed for those that are saved for the form with the upload field.
Each time you remove the submission with a file, you are removing that file as well and as you remove it it will clear out your storage space.
Please do make a backup of any data that you might need at a later point, before removing the data from your account.
Let us know if you need any further assistance.