Issue of generating AWS signature

Hi there. I tried to make AWS signature in a scenario but there seemed to be an issue in generating signature(Authorization).
However, Stoplight always returned error about fail of specifying credentials.
This is an error message:

{
  "message": "Credential should be scoped to correct service: 'execute-api'. "
}

I got signature by AWS keys & token in auth tab in step and pushed Update Request. This is an example of signature(partly censored).

AWS4-HMAC-SHA256 Credential={$.ctx.AWS_ACCESS_KEY_ID}/20200109/ap-northeast-1//aws4_request, SignedHeaders=content-type;host;x-amz-date;x-amz-security-token;XXXXXXXX;XXXXXXXXXXX, Signature=XXXXXXXXXXXXXXXXXXXXXXXXXXXX

I compared this one with another one which was made by postman(but same keys), Spotlight one didn’t have execute-api between two consecutive slash(//).
Is this how it’s supposed to be?