custom zoom from ggmap

I couldn't quite figure out how to customize the map extent from a Google map:

I'd like the map extent to just surround the color overlay in the middle. in get_googlemaps this is scale 8, and scale 9 is zoomed in too far.

My code is:
ggmap( map ) +
geom_sf( data=nr , fill=NA , color="Darkred" , cex=1.5 , lty=2 , inherit.aes = F) +
geom_tile( data=pred , aes( Longitude , Latitude , fill=Estimate ) , color="NA" , inherit.aes = F) +
scale_fill_viridis( option="A" )


Thanks!