The updated numbers are starting to appear on the map. Can be a bit confusing as different tiles are updated at different times for different zoom levels. Should all be aligned in 24 - 48 hours
Fairly easy to add numbers using the iD editor that is accessible from https://www.openstreetmap.org and there are smart phone apps designed to make collecting information easy (even fun) by treating the surveying as quests. Examples https://every-door.app/ and the very popular https://wiki.openstreetmap.org/wiki/StreetComplete
Surveying on the ground is always helpful, one must never copy from other maps but updating based on local knowledge and from on the ground surveys will help improve the map.