Why is AWS S3 Object count is measured iin units used to measure file size?
You have shown a screenshot of your Storage Lens account snapshot, which gives you a summary of what is in all the S3 buckets in your account.
You can see that you have consumed 3.2 petabytes of storage using 2.3 billion objects with an average object size of 1.5 megabytes.
In this case the G simply means giga, or billion.