"Distances" attribute in OC20 dataset IS2RE task

Hi,
I am attempting to predict Bader charges from the OC20 dataset. However, the ‘distances’ attribute in the OC20 IS2RE dataset, which takes the form of a 1D array, is not defined in the READ_ME File. What does each value in the array correspond to? Is it the distance between two atoms, and if so, how can I determine which two atoms?

Thanks so much!