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.
JotForm Support Manager
You can easily do this, by selecting the field, then going to the toolbar.
For example, if you want 10 MB, then you must enter 10240, because the size it's set on KB.
In addition, here are some guides that might be useful :