explaining FilePut method

Question

I am using this method(): Microsoft.VisualBasic.FileSystem.FilePut(file_num, "aaa",-1)
and would like to know what '-1' can mean. 
MSDN writes it is "record number (Random mode files) or byte number (Binary mode files) at which writing starts". It does not make sense as there is no -1 record.
However, the code snippet works fine.