webform_number_limit
This module provides Webform handlers that allow forms with a number element to have submission limits based on the sum of those numbers. It's similar to the Options/Checkbox limit handler provided by the Webform Options Limit official submodule, but instead of counting every submission as 1, it allows that number to be taken from a number element.
A practical application would be a registration form with the possibility to not just register yourself, but to also bring a certain amount of guests, while making sure those guests also count towards the maximum amount of registrations.
Post-Installation
After installing the module, add one of two Webform handlers to your webform. The Number limit handler can be used to set a maximum amount of registrations per form, while the Options/Checkbox with number limit handler can be used to set a different maximum amount of registrations depending on the chosen option of a certain options or checkbox element.