TCP segment of a reassembled PDU

A "PDU" is a "Protocol Data Unit." One unit of information being transferred in accordance with a given protocol (e.g., "login USERNAME very-long-base64-encoded-authentication-data" then wait for server to respond) will be disassembled into many packets (smaller pieces) if it's too large to fit in one packet (or segment in this case).

This is normal and is just TCP/IP working as designed.