You can post transactions to add or subtract to these boxes both 6 & 7 by using no vat code or exempt.
Boxes 6 & 7 are never 20% of the boxes 1 & 4 where to Vat codes other than standard 20% are used, reduced rate zero rate and exempt all post to these boxes.
Boxes 6 & 7 include all sales & purchases so anything here from outside Eu is here and not subject to Vat.