Extra Warning field in Ver 1.7.2 for Encode function in ADP

Notice now there is an extra field on the encode respond

–header “X-Vault-Token: …”
–request POST
–data @payload.json

“data”: {
“encoded_value”: “5682-4613-6822-8064”
“warning”: “” << Extra warning field

What is this and what condition will trigger a warning message? I couldn’t find any document or release note that explain this field