These are regions marked up on the genome to allow curators to identify the likely start and end of a gene in combination with other features such a ATG and polyA features. These regions occur where there is more than 5 times the number of reads from the reverse sense of the RNA than the forward sense. These asymmetric read regions are characteristic of the start or end of a transcript. The value stored in the corresponding feature is the sum of the number of reads observed in this region from all aligned RNASeq libraries. This data is available in the gff3
with this source/method combination [RNASeq_(F/R)_asymmetry transcript_region].