Since latest update, Inbox shows red unread emails?

The +4 means by default means"recent" messages in the new eM Client V10 for messages in the various Category inboxes. You can set in Settings to have either recent or unread in the Categories or you can disable the counter. See the below thread on the subject.

I don’t know what the blue number means, but another forum member will know that and update this thread.

Also as to where your missing emails are. See my post link below on the following thread.