[galaxy-user] Is tss_id unique for each transcript?

Dear All, I am reading and comparing the outputs of Cuffdiff. I found there is a "tss_id" column in "transcript FPKM tracking", "gene FPKM tracking", "TSS groups FPKM tracking" and "CDS FPKM tracking" files. In this column, each line has a unique label such as "TSS1001". This kind of labels also appear under "test_id" column in "TSS groups differential expression testing" and "splicing defferential expression testing" files. Does each of this kind label represent a unique transcript? In other word, does each transcript has a unique label initiating with TSS followed by numbers? Thank. Jianguang