As an Indian who moved abroad and comes back occasionally this is the hardest part. As an Indian I always think in multiples of 10: 100,1000,10000, 1 lakh etc, but abroad after a certain point people think in multiples of 1000. 1000, million, then multiples of 10..The Indian system to me is more logically consistent
My wife is chinese and they have a very commonly used word for 10,000 so when she needs to say either 10,000 or 100,000 she almost always gets it wrong and says 1,000 instead of 10,000 and says 10,000 instead of 100,000. It's happened so often I mentally translate automatically if it's clear from context.
The Indian system is clearly less consistent from an outsider PoV: You use a 3 digit gap for the first comma, then 2-digit gaps (1 crore is 1,00,00,000); the western system is consistently 3-digits (1 million is 1,000,000).
