houtari
I guess you're referring to the OSM carto map style (available on openstreetmap.org) which visualises what's defined under the road's ref tag? In Finland this part has primarily another official road numer (959) and that's also the value that's been entered under the ref tag. This finnish part does have the E45 value under the int_ref -tag. This is how we've decided to enter the data in Finland as these national road numbers indeed are the primary ones and are as a rule placed above the European route numbers. Eg. Käsivarrentie that goes through Karesuvanto northeast-southwest -bound is labeled 21 but it's also E8, So at this point I don't see a reason to change anything here.