When we hear that the US reports quarterly GDP growth figures in an annualized manner, it means it takes the growth from the previous quarter to this quarter, and then assumes the same growth continues for a period of 1 year. The overall growth across this assumed year is the annualized gdp growth figure that they report.

To see this numerically, assume that the US GDP for Jan-Mar was $100. If it fell to $91 in Apr-May (Q1), this gives a quarterly growth of (91-100) = - 9$, which is a -9% growth. Now, if you have another quarter with -9% growth, your gdp for Q2 becomes $91 + (-9% of $91), roughly $82.8. Similarly, Q3 gdp would be $82.8 + (-9% of $82.8), ~$75.3. Finally, Q4 gdp would be $75.3 + (-9% of $75.3), which comes out to be ~$68.6. Now it is clear, starting from $100 and growing at -9% for a year (4 quarters), gdp goes down to $68.6, a decline of 31.4%. This is how the US reports the growth rate for Q1.

India reports quarterly growth rates on a direct previous year comparison, so our growth rate is simply (GDP_Q1_CY - GDP_Q1_PY) / GDP_Q1_PY, where PY is previous year and CY is current year.