Question about Load Test output

Hello all.

I have a working Load Test set up on SoapUI that for some reason is not resulting as I expect. Either that, or I'm misunderstanding how it works!

Here's how it's set up:

Threads: 20

Strategy: Simple

Delay: 1200ms

Random: 0.2

Limit: 600 seconds

My understanding is that the 20 threads will make each POSTs request (the batch of seven) every 960~1200ms, or roughly 140 requests per second. However, the outcome is rather different: about 12 POSTs request per seconds instead of the expected ~140.

What am I doing wrong? Is something on my configuration? Am I misunderstanding how it works?

If this is the wrong approach, how can I best emulate a load of about 100 request per second?

Many thanks for any advice!