Are Runscope Scheduled Tests sequential or Parallel?

Here is my situation . We are testing our API with runscope . the main steps are follows .

• Create an Order by User
• Driver Take the Order
• User Cancel the order taken by driver

This process takes around 3 minutes to complete , i want to run a scheduled job for this test every 1 minute . 

If scheduled jobs run parallel my tests will start and finish like this .

test 1 | start at minute 0 | finish at minute 3

test 2 | start at minute 1 | finish at minute 4

test 3 | start at minute 2 | finish at minute 5

test 4 | start at minute 3 | finish at minute 6

so there will be no problem . 

But if jobs run sequential what will happen is there will be lots of queued jobs in Runscope . because one test will take 3 minutes to complete but we run tests every 1 minute .

so i am afraid that runscope will run out of memory or give an error if the Queue is too large ( Actually i don't know hoe runScope will handle this situation . )

I cannot test this situation because "Test schedules require a paid Runscope subscription." , And i don't want to pay without knowing how Runscope will handle the situation . 

Please help me to understand how runscope works in this kind of situation .

Thanks in Advance.