The Series by SOF report must use data from top split only.
When done properly, for Mazda, the SOF would approach 3000:
https://iracingreports.com/stats/24s4-Global_Mazda_MX-5_Cup.html
This is actually one of the more competitive series on iRacing.
However, in your results, the Mazda series is bottom of the list with 1300:
https://json.racing/irs/24s4/sports/series/