If you're remitting less than Rs. 7 lakh for investing in US stocks, you'll pay ZERO TCS.
If you're remitting more than Rs. 7 lakh for investing in US stocks, you'll pay TCS of 20% on the amount exceeding Rs. 7 lakh. For instance, if you're remitting Rs. 9 lakh for investing in US stocks, you'll pay TCS of Rs. 40,000 (20% of Rs. 2 lakh) on the Rs. 2 lakh that exceeds the Rs. 7 lakh limit.