It's because they've got a different counting system. 1 lakh = 100,000. 1 crore = 10,000,000 (or 100 lakh).
We write numbers like 123,456,789, so one hundred and twenty three million, four hundred and fifty six thousand, seven hundred and eighty nine. They would parse the same number as 12,34,56,789 - twelve lakh, thirty four crore, fifty six thousand, seven hundred and eighty nine. These also stack, so where we'd parse 1,000,000,000,000 as one trillion, they'd parse it as 10,00,00,00,00,000 or one lakh crore (one hundred thousand ten millions).
Based on how they learn maths, they probably struggle switching between numbering systems. It also probably doesn't help that various Indian languages have their own unique numerals
View attachment 8572339