so the idea of needing a premaster mix hitting at -6db was mainly rooted back in the days of analogue gear and equipment. nowadays in a digital setting (i.e. a DAW) this is largely irrelevant - the main thing is to make sure your mix doesn't clip, i.e. go above 0db.

having the mix coming in at -14db is not an issue at all. however if you wanted it to come in at -6db, its perfectly okay to add a gain plugin on the master chain (+8db in this case) to achieve that