Do not obsess over the history log. The reason it exists is for us to be able to debug CBSubs issues. Most of it will sound like gibberish as it's just logging status changes for the most part. Unless you're having any actual issues with your site it's safe to ignore.
1 2019-05-07 08:46:02 Change log User subscription record created with status: I User subscriptions 262 insert
This means a user subscription was inserted into the database with an ID of 262. The status of that insert is I (invalid), which is the status a subscription is in if it's reversed typically.
1 2019-04-25 06:51:22 Error log loadSomething::subid 252 with planid 1 could not load.
Means the subscription with an id of 252 has a plan id of 1 that can't load. Either the plan doesn't exist or the subscription doesn't exist.