KiCad 5.99 trace length tuning

Hi all,

Pretty new to KiCad, but have used other EDA tool previously. First time I am using KiCad to tune trace length. Had it set to tune each track to 12mm and it appeared to work fine, but the strange thing is if I click on the “tuned” traces with the tool after I set the length required, it then tells me the trace is longer or shorter than specified.

Example in the attached image, this trace was set to 12mm give or take a about 0.05mm but now it is “Too Long” and 0.8mm out of spec.

What is going on here? Is it me, or just a bug in 5.99? Full version I am using is: (5.99.0-11663-g8172737d6f), release build.

Thanks