Webforms: Attribute “size” not allowed on element “input”

Number fields in webforms are showing the error 'Attribute “size” not allowed on element “input” at this point' in Web Audit. 
Ex: https://webaudit.unl.edu/sites/835/pages/10622556/ 

I think the input should have a 'maxlength' attribute instead of size: https://www.w3schools.com/tags/att_input_size.asp