Franchise sales (without counting Tourist Trophy) were 77,020,000 units as of September 30, 2017, Gran Turismo Sport (released in October 2017) brought an additional 12,977,000 units as of seemingly late 2021, which makes the total number 89,997,000 units.
Gran Turismo 7 has sold,
at least, 3.440.000 units across retail and digital in the US as of January 4, 2025, while
retail only sales in Japan are of 565,386 units as of June 15, 2025 (PS4 sales as of June 1, 2025). The game also received a platinum award in January 2023 for selling over 400,000 units (retail+digital) in Germany, and plus the 30,000 retail units it sold at launch week in Spain, we have,
at the very least, 4,435,386 units we know of Gran Turismo 7. Which also means that we, at least, have a semi-official number of 94,432,386 units for the Gran Turismo series.
GTPlanet has estimated around 14,400,400 units sold of Gran Turismo 7 (which I agree with), which would put the number at 104,397,000 units, but you can use 94M for now.