Why tests still taking very long time to run with Cypress Dashboard

[Jeffintel]

Hi Folks,
would like to ask a question re: Cypress Dashboard.
I have a project that takes 4 hours to run in Serial.
I now have Cypress Dashboard and use Parallelisation with 8 machines, but still, taking 1h30 to finish the test. Is this normal?
with 8 machines in parallel, I would expect the test to be 8 times faster.
Thanks in advance for your help.