Lambda not scaling enough with SQS queue trigger

I have an SQS queue set up as a trigger for a lambda function. In the trigger settings, the maximum concurrency is set to 100, however when the queue has tens of thousands of messages in it, the lambda never scales to concurrency greater than 10. I have no other lambdas running, so shouldn't it be able to scale as high as 1000 if that were the concurrency limit on the SQS trigger? How can I get higher concurrency when the queue is full of messages?