The 5 "petaflops" number is a creatively constructed marketing number based on FP16 TensorCore "flops", sparse matrix calculations, and then multiplying by 8x for some reason. They basically take the 19.5 FP32 TFLOPS number and multiply it by 32x to get to the claimed 624 "TFLOPS" for a single A100. 8 * 624 = 5 "petaflops". I see they get 2x by actually using FP16 instead of FP32, 2x from counting sparse matrix ops as dense ops, and 8x from somewhere else that I have no idea.
[1] https://devblogs.nvidia.com/nvidia-ampere-architecture-in-de...
[2] https://www.top500.org/resources/frequently-asked-questions/