Keywords not display in source and also i am unable to add more then 5 keywords

Respected sir
i have install Rank Math and i found it very useful but i am facing few problems
1. when i check my SEO score showing me 61/100 before keywords when i add keywords still its show the same.
2. Rank Math did not allow me to add more then 4 or 5 keywords
3. when i add keywords its not show up on website source page.
i will be very thankful if you solve my issues.
thanks