Documentation: Confusing graph

Describe the bug
I just looked at the front page of this package's github. I glanced at the readme, and I saw a graph. It compares different ORM's to Tortose. The graph itself doesn't appear erroneous, but the y-axis isn't labelled, and there's no surrounding explanation of what's being compared. Is performance is clock cycles? Nanoseconds? I am not sure if lower is better, or higher is better. I appreciate it seems to be an objective comparison across different ORM's, but I don't know what performance metric you are benchmarking against.

I won't discount your package based on something so small, but as someone who works with data in an analytics capacity, this damages credibility from what otherwise seems like a fantastic tool.

To Reproduce
Check your front page Readme.

Expected behavior
A labelled y-axis which indicates your performance metric, or an edit on the sentence above explaining what the y-axis intends to measure.

Additional context
I skimmed https://github.com/tortoise/orm-benchmarks and while there's a lot of raw data, I still am left unsure about how to interpret these results. I think it's a good idea to include these things, but a small explanation about what they mean can help outside people who are curious about this project.

Inspect the graph on the project's front-page README and compare it with the raw data in https://github.com/tortoise/orm-benchmarks. Determine which performance metric and direction the graph uses, then update the README with a labelled y-axis or a concise explanation. Done means a reader can tell what is being measured and whether higher or lower values are better.