Does this FASTQ data contain single or paired end calls?
Entries in a fastq file occupy 4 lines each and R1 and R2 are typically in different files. Since that SRA project is 2x51 you seem to have run fastq-dump without the --split-3 option, so both R1 and R2 are merged together. Make your life easier and never use SRA, but instead just download the individual files from ENA.