How to compare double type filed in logstash output

Elastic Stack Logstash
5

But I can see the fields in kibana under available fields have a look on my config

input {
    exec {
    command => "redis-cli info clients"
    interval => 4
    type => "clients"
    }
   exec {
command => "cat /proc/meminfo"
type => "sysmem"
interval => 4
}  
    exec {
    command => "redis-cli info memory"
    interval => 4
    type => "memory"
    }
     
    exec {
    command => "redis-cli info cpu"
    interval => 4
    type => "cpu"
    }
     
    exec {
    command => "redis-cli info stats"
    interval => 4
    type => "stats"
    }
     
    exec {
    command => "redis-cli info replication"
    interval => 4
    type => "replication"
    }     
    }
    filter {
    split {
    }
     
    ruby {
    code => "fields = event['message'].split(':')
    event[fields[0]] = fields[1].to_f
    "
    }

    }
     
    output {
          elasticsearch {
        hosts => ["localhost:9200"]
      }
 if [MemFree] and [used_memory_human]
{

if [MemFree] > [used_memory_human]
{

}


}
stdout { codec => rubydebug}
}