Using flux YAML, how to mention number of task for bolts in a Storm topology?

Question

See this snippet of storm-flux YAML:

## spout definitions
spouts: 
#spouts- Start
  - id: "perform-spout"
    className: "org.apache.storm.kafka.KafkaSpout"
    parallelism: 2
    constructorArgs:
      - ref: "PerformSpoutConfig"
#spouts- End  
   
## bolt definitions
bolts: 

#bolt - Start    
  - id: "perform-bolt"
    className: "com.cc.adv.asp.test.KafkaPerformanceBolt"
    parallelism: 2      
#bolt - End    

With this script, Storm-UI shows No. of executors=No. of tasks. Please suggest how to specify no. of tasks in Flux YAMLs? Thanks in advance.