The title of "Section 5.2 : CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port fields" looks like the section refers to 3 different option field, but the text in it uses the singular form and mostly describes the Max-Age option.
Some rewriting is needed, but I'm not familiar enough with CoAP options to be authoritative here.
The title of "Section 5.2 : CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port fields" looks like the section refers to 3 different option field, but the text in it uses the singular form and mostly describes the Max-Age option. Some rewriting is needed, but I'm not familiar enough with CoAP options to be authoritative here.