From a climate-change only perspecitive, the original paper actually says that if you re-use a cotton bag just 53 times, you're already doing measurable good, and if you keep using it you keep doing more measurable good.
The higher number come from value judgements about other kids of impacts, and reasonable people can disagree over the relative values of those impacts vs climate change.
The higher number come from value judgements about other kids of impacts, and reasonable people can disagree over the relative values of those impacts vs climate change.