You're not reading it completely wrong. There is a beta decay. Look at the last page of this table: http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_tables.pdf

You're not reading it completely wrong. There is a beta decay. Look at the last page of this table: http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_tables.pdf http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_tables.pdf The green arrows are possible beta decays to lead 208. But 208Tl never decays to the nuclear ground state of lead 208. And so after the beta decay, there are gamma rays (the black arrows) as the nucleus relaxes from whatever excited state it ended up in.