mm, not sure how to advise this, without looking like a simpleton...
Checked the back Mud Guard stays on my bike and found the tab in question, however it is on the otherside!.
I remember contemplating which way round the stay went and decided the way I have it, made the lifting handle easier to operate.
Drag's diagram didn't look correct to me.
Only excuse I have is we are, after all, located on the otherwise of the world to the UK where the bike was designed and manufactured.
Upside down as it were.....
Now I have a job for the weekend.
1946 VB600 rigid Tele
1933 Austin 10
2008 Fraser Clubman (like lotus 7 only better )