How exactly do you even measure the GDP of such an ancient empire? Economists can't accurately measure GDP of western economies today despite huge armies of statisticians, even China's true GDP is a mystery, so I'd have to assume any such claims about the GDP of the Mughal empire are nonsense.
Additionally Mughal rule in South Asia stretched from what is modern Pakistan, to Kabul in Afghanistan and Bengal in the East. So the idea that there would been numbers specifically just India is kind of ridiculous.
