One line under the name Surdas appears in the Guru Granth Sahib Ji, in Sarang, followed by a completion by Guru Arjan Dev Ji. It is the shortest contribution in the volume.
The Surdas of the Guru Granth Sahib Ji is generally taken to be Madan Mohan, a Brahmin who was governor of Sandila in Awadh under Akbar and who left office, rather than the blind poet of Braj whose Sur Sagar is the great Krishna devotional corpus.
The two are confused constantly. The identification is not settled and the volume gives no help.
That a single line was kept, and completed by a Guru rather than discarded, says something about the editorial principle at work in 1604.
The line itself is an instruction to leave the company of those who take you away from what you are doing, and it stands complete as a thought, which is presumably why one line was enough to keep.
The completion by Guru Arjan Dev Ji is signed and is longer than the fragment it completes. Whoever the original author was, the volume treats one surviving line as worth keeping and worth finishing, and the join between the two hands is there on the page for anybody to see.
The volume does not settle which of them it means and the editors who assembled it left the attribution as it stood. That is itself evidence about how the compilation treated its sources, which was conservatively.
Guru Granth Sahib Ji, Sarang.