PC Leaderboards won't recognize my Setup as DEFAULT

[Xiamoto]

Does anyone know how to "reset" a custom tune so that the PC Leaderboards will recognize it as a DEFAULT tune? I've tried the obvious procedure to "reset" all car/ffb settings to their default values and then saving those values to the targeted circuit........but after recording a time trial lap time ........the PC Leaderboard displays my data as as having a "C" .....custom tune.

Thanks in advance for any info you can provide....cheers!