For single-end reads, use F or R. 'F' means a read corresponds to a transcript. 'R' means a read corresponds to the
reverse complemented counterpart of a transcript. For paired-end reads, use either FR or RF. (TopHat has a similar
option[see details below link], --library-type option, where fr-firststrand corresponds to R and RF; fr-secondstrand corresponds to F and FR.)
Indicate if strand-specific read counting should be performed.
Acceptable values: 0 (unstranded), 1 (stranded) and 2 (reversely
stranded). 0 by default. For paired-end reads, strand
of the first read is taken as the strand of the whole fragment.
FLAG field is used to tell if a read is first or second read in a
pair.