"Failed to parse Timestamp. Defaulting to file modtime"- Error message

Hi, It will be so helpful for me, if anybody could give a solution to the following question When i am trying to parse the data into splunk before indexing, the timestamp of the events were not identified properly and it is showing "Failed to parse timestamp. Defaulting to file modtime" what should i do now to resolve this. The timestamp in the log events are in the format of 201908162035357024.00 that is 2019-08-16 20:35:35