There are lots of local guides who generally ask about drive space problem/perk. It is because photos uploaded to map really eating their space. I also faced the same but now everything will be alright. There are lots of thread in connect with drive perk/drive space problem but I never found the words mention below.
1. When you’ll upload photos on map it will be count against your drive space.
2. For making space in your drive visit to https://photos.google.com/settings and choose High quality (free unlimited storage) [This is safe and will not affect your contribution on map].
3. Now many local guides will say that they already selected that option, but it does not matter( that’s why I started this and this) and for making space in your drive you have to press the compress button into this link. For quick solution here is a video link.
I think that a couple of photos can explain in a very easy way that “photos loaded in Maps” is not issue for the use of the space.
In addition I can say that (in my case) the space was removed after 1 year. Honestly I was waiting for that moment, I’ve transferred a lot of photos from GDrive to Gphoto. Now I’m going to transfer also the photos that still in drive, I think I well free other 4Giga of space.