I had a similar discussion with the AWS Glue support team about this, I'll share with you what they told me about Glue Configuration. Take in example the Standard and the G1.X configuration.

Standard DPU Configuration:

• 1 DPU reserved for MasterNode
• 1 executor reserved for Driver/ApplicationMaster
• Each DPU is configured with 2 executors
• Each executor is configured with 5.5 GB memory
• Each executor is configured with 4 cores

G.1X WorkerType Configuration:

• 1 DPU added for MasterNode
• 1 DPU reserved for Driver/ApplicationMaster
• Each worker is configured with 1 executor
• Each executor is configured with 10 GB memory
• Each executor is configured with 8 cores

If we have for example a Job with Standard Configuration with 21 DPU means that we have:

• 1 DPU reserved for Master
• 20 DPU x 2 = 40 executors
• 40 executors - 1 Driver/AM = 39 executors

Which we then end up with a total amount of 156 cores. Meaning, your job has 156 slots for execution. If for example you read files from S3 that means that you will be able to accept 156 input files in parallel.

Hope it helps.