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 should at least provide more details about your inquiry so that we can provide you with the appropriate suggestions and solution.
I am not sure what you meant about the form length, but I can only assume it is about the form height.
There are 2 ways to achieve that.
#1 Using the Iframe embed code you can adjust the iframe height value.
<iframe allowtransparency="true" src="//www.jotform.com/form/1222222" frameborder="0" style="width:100%; height:100px; border:none;" scrolling="no">
#2 Using custom Injected CSS codes, you can add CSS code to assign height to the form
Check this similar thread http://www.jotform.com/answers/290351-How-can-I-change-the-width-and-height-size-of-my-form
Hope this help. Inform us if you need more assistance.