Getting error as "customfield_17431":"Operation value must be a number"

[Ravi Kanth Tadoori]

Json Body in confiform 

{"fields": { "project": { "key": "DCIPTQA" }, 
"summary": "[entry.nameofproject.fullName]", 
"description": "[entry.description]",  
"customfield_17431":"[entry.automatedTests]",  // numeric value

Error :

com.atlassian.sal.api.net.ResponseException: Error communicating with Jira,
{"errorMessages":[],"errors":{
"customfield_17431":"Operation value must be a number",