As you probably saw it, we released CentOS 7.7.1908 for all
architectures earlier today :
-
https://lists.centos.org/pipermail/centos-announce/2019-September/023405.html
-
https://lists.centos.org/pipermail/centos-announce/2019-September/023406.html

Just after that we regenerated the koji internal repos to use that new
release so it's now done :
https://cbs.centos.org/koji/tasks?state=all&owner=koji&view=flat&method=createrepo&order=-id

That means that all your builds for CentOS 7 will be built against
7.7.1908 content.