The VideoCore VII GPU does not have its own VRAM, it's only a compute chip. From the Hackster.io review[1]:

> The chip also features a new Broadcom Videocore-VII graphics processor running at up to 800MHz, and is linked to the buyer's choice of 4GB or 8GB of LPDDR4x memory.

https://www.hackster.io/news/raspberry-pi-5-review-hands-on-...