How many records should I aim to put into a DynamoDb partition?

We have an AWS Batch Job, which runs on EC2 instance:
Instance Type: c6g.medium
vCpu: 1
Memory: 1 GB

I am trying to delete an item in a dynamodb table. Even if I provide the correct id, the command rejects it:

I am trying to delete an item in a dynamodb table. Even if I provide the correct id, the command rejects it:

I am getting a “The provided key element does not match the schema” and I don’t quite understand why.

I´m facing the following problem:

I am looking for help on design the dynamodb table. Here is my usecase,