you can use 4.7 gb if its written 4.7 on the disc. upto 4.5 gb is the safe option... 4.7 can be used with a software that supports overburning.. but it should only be done when required. the safest option is to burn till 4.3 gb. 4.5 gb is fine, and in 4.7 gb the burning will be done almost upto the last millimeter from the outside of the disc..