For the RNA-Seq analysis, i am using paired-end datasets that has been generated from Illumina HiSeq 2500 (Homo sapiens). I have used the following command for quantification,
featureCounts -F GTF -t exon -g gene_id -O -s 0 -a 'GRCh38.96.chr.gtf' -o count_from_ensembl.txt SRRXXX*.bam
In output, both '+' and '-' strand are there in the strand column. I am not able to understand whether its correct or not. Is illumina Hiseq 2500 is strand specific? if not, then how to know whether the reads are stranded or unstranded?