No worries, it just a warning not an error. It mean that coder is unable to recognize the data type of the variable and hence treats it as a string.
To disable this info, do below
Navigate to IS Admin Console(all IS that connects to MWS) > Settings > Logging > Edit Server Logger > Facility: Integration Server >> 0088 SOAP = Error
Restart all IS that connects to MWS.
#webMethods#Integration-Server-and-ESB#B2B-Integration