Random numbers being printed back after entering data
The problem is that you are blindly reading serial data without first looking to see if there is actually any serial data available to read.

If there is no data there Serial.read() will return -1.  Since you have only provided a snippet of your program I can't say what data type inbyte is, but my guess is it's some form of unsigned 32-bit value, since -1 mapped into an unsigned 32-bit value is 4294967295.

You need to be checking the presence of data, and only reading when you should read, and also looking for the end of your data sequence (add some terminating character, like a line feed) to know when to stop looking for and reading characters.