Google Colab: RuntimeError: CUDA out of memory

Question

I'm playing with Create Realistic AI-Generated Images With VQGAN + CLIP which is a notebook on Google Colad.

I am generating images and wanted more resolution that 600x600

I have purchased Colab Pro+ as I understood this would give me more memory and a better GPU.

The notebook is reporting I am using a Tesla P100-PCIE.

I am getting this error:

CUDA out of memory. Tried to allocate 358.00 MiB (GPU 0; 15.90 GiB total capacity; 14.52 GiB already allocated; 211.75 MiB free; 14.69 GiB reserved in total by PyTorch)

I do not know how to read this.

I have looked at a number of videos and tutorials but they are either written from the point of view of someone who already knows what how Colab works or are very simple cut down step-by-step instructions.

There is this Stack question: No additional memory from Colab Pro+ but it doesn't answer my question.

What does the message mean?

Why does it occur?

What can I do about it?