Rank Tracker updates your keywords based on when you've added them.
Here's an example.
Imagine that you're on the Lite plan (i.e Rank Tracker updates every week), and you're interested in tracking 2 keywords:
- seo tips
- keyword research
If you added "seo tips" on 14-Sep and "keyword research" on 15-Sep to Rank Tracker respectively, then "seo tips" will update on 21-Sep and "keyword research" will update on 22-Sep.