Too many messages in flight

Hi,

I have an SQS-consumer (https://github.com/bbc/sqs-consumer) running on an EC2 machine (t2.medium). There is only one instance of this process running at the time. However, when I open my SQS dashboard I see more than 30 messages in flight. It's a FIFO queue, with deduplication based on MessageGroupId. I'm not using any batching the library offers, just simple consumer one message at a time as the library tutorial shows. What am I missing here?

The reason for concern is that I'm getting A LOT of timeout errors when processing messages (I'm using Puppeteer to open websites and check for links on them) - and I'm trying to narrow down the cause for this - and overloading the t2 machine network bandwidth might be one of them (I think).