Are you trying to get the topics count or messgaes (reply included) count?
I'm trying to get all post including messages (and replies). So the absolute total of posts on the community.
Try these two API. You should get the approx. similar count.
https://community.lithium.com/api/2.0/search?q=select%20count(*)%20from%20messages
https://community.lithium.com/restapi/vc/posts/count
Also, I would suggest you contact with lithium support to know it in detail. Find the helpful link here
https://community.lithium.com/t5/Developer-Discussion/Support-for-Elastic-Search/m-p/436976#U436976
Thank you for the two API calls, but why can't i get this from the LSI? or am I looking at the wrong metrics?
