I see. That paper is looking a median income from a PPP perspective but without accounting for taxes and transfers, which is a tiny bit unorthodox in this exact context which tries to get into the weeds slightly more than just standard PPP adjusted GDP per-capita or something like that. It's valid statistically, but typically if you're trying to adjust for cost of living it makes a lot of sense to use the amount of actual income the individuals have left over after paying taxes and receiving transfers from social programs. Otherwise you'll have a number which accounts for differences in prices but not differences in the proportion of "income" which is actually retained by the earner. This is what that wikipedia article I linked is reporting. Comparing two different countries with very different tax/social program policies with PPP adjustments but without tax/transfer adjustments is less than ideal.

It's not wrong, it's just not very useful. It's typically a more intermediary statistic rather than a final one when doing this type of comparison.