Jenkins EC2 multiple spot instances

[York Sun]

I need some help on Jenkins EC2 spot with multiple instances. I try to setup the cloud with C4x8, M4x10 and other types, hoping to catch the less expensive spot price. Sometimes c4x8 is cheaper and sometimes m4x10 is cheaper. However, I never see my m4x10 instance starts. It always waits for c4x8 which is my first instance in configuration. I can only start my m4x10 instance by using different label. This is not the case I want to discuss.

Is it even possible?