I have configured 2 AWS clouds, for example (prodVpc and devVpc) in different regions with 1 AMI in each (with different names)

It said that 'Minimum number of spare instances' and 'Minimum number of instances' act on per AMI basis.

Configuring:

> Minimum number of instances=1

> Minimum number of spare instances=1

for each ami/cloud i've expected to get 2 ec2 slaves in total:
1 for prodVpc and 1 for devVpc.
I get only one ec2 slave instead.

Changing these parameters values up and down and running jobs i've made a conclusion, that plugin takes in account the total number of fired up by plugin instances, regardless to Cloud name or AMI id.