I have tested this furthar and I believe there is a problem/error with different behavior while you use the Optional parameter « Limit the amount of voters per option ».
In the pooling mode, it allows the « green vote » up to this limit while in the « edit » mode (after clicking the pencil icon), the Limit the amount of voters per option is considered for all the votes regardless of the symbol (so it counts even for the empty vote -"?").
Can someone confirm my understanding and findings? This feature is not documented much