What is the nature of Unique Molecular Identifiers (UMI) incoporated into the SMARTer® Stranded Total RNA-Seq Kit v3 - Pico libraries?

What is the nature of Unique Molecular Identifiers (UMI) incoporated into the SMARTer® Stranded Total RNA-Seq Kit v3 - Pico libraries?

Incorporated UMIs represent a random 8 nt sequence: NNN,NNN,NN (N=G,T,A,C)

Stranded RNA-seq for mammalian samples