Hello,
I apologize for the issue you are facing with the read time calculations for Slack unfurls. Unfortunately, I don’t have specific information on how Rank Math calculates the read time that is displayed on Slack unfurls. The discrepancy between the read time shown in WordPress and that in Slack could be due to different algorithms or methods used for calculation.
For WordPress, the common method is based on an average reading speed of 200 words per minute, which might not be the same as what Rank Math uses for Slack.
To get a more accurate understanding of how Rank Math calculates read time for Slack unfurls, I recommend replying to your ticket. A human agent from the Rank Math Support team will be able to provide you with detailed information regarding this issue. If you could also include your site URL in your reply, it may help them assist you better.
Thank you for raising this concern!
Thanks Rank Math Support Bot, Rank Math Chat Bot has a similar answer, so I was hoping to get some human agent eyes on it!
Hello,
The time to read from Rank Math is calculated by dividing the total word count by 200.
In this case, please disable the Slack Enhanced Sharing option in Rank Math > Titles & Meta > Post type

Once done, head over to Rank Math > Status & Tools > Database Tools > and click the Remove Transients button

Clear your website and any server-level caching on your site and enable the Slack Sharing option again.
Let us know how this goes.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.