I got the answer from 10x Genomics Support. BTW, they were very quick, kind, and helpful. Well, if somebody needs the answer in the future, here is the one from the 10X Genomics:

" Gaps captured by read pairs are 100Ns.Cycles are broken and prefixed with 10Ns the larger gaps are estimated using the barcodes as described in the supplementary file www.biorxiv.org/content/early/2016/08/19/070425.

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