...

Subsample FASTQ is only available for unaligned reads of FASTQ format. To trigger this function, select the Unaligned Reads data node and select Subsample FASTQ from the Pre-alignment tools section on the menu. Then specify how many reads you want to keep for every nth reads. For example: if the user specifies to "Keep one read for every 10 reads" (Figure 1), this means that for every 10 reads, the program will keep only 1 read. This is equivalent to keeping 10% of the data. 

...