What do negative delay time in files of tree folder represent?

[bazarijoo]

Hello,
Thank you for sharing the source code. I wonder, in tree folder some files like 752965545528528898.txt, there exists some propagations with negative delays. What are these delays? Also, in some files, there are some propagations before reaching the root. I read README in the original dataset, but did not understand their presence.

['14499829', '752934272500109313', '-124.27']->['14499829', '752934272500109313', '-124.27']
['ROOT', 'ROOT', '0.0']->['14499829', '752934272500109313', '-124.27']
['14499829', '752934272500109313', '-124.27']->['2293496059', '752965545528528898', '1.1']
['14499829', '752934272500109313', '-124.27']->['267252690', '752965545528528898', '1.1']