That's a great question. I found a related note the team has on the topic.
Regarding the current limit it reached in that table. There's a possibility that if some records were never added but were sent to that webhook, it counted them towards the overall limit or some of the older records were manually removed at some point.
The scenario where you wouldn't encounter a webhook limit is when an the hook is attached to a table that has auto-delete enabled which allows it to remove the standard 50k record limit. Otherwise, if you're looking to keep the data in that table, it would be best to duplicate this table, it will allow you to start a new table with the same logic without any of the data, and to create a new webhook for that new table.