Simple ratio strange behavior

[radio1988]

#A 
>>> fuzz.ratio("13245", "12345")
80

#B 
>>> fuzz.ratio("13345", "12345")
80

#C 
>>> fuzz.ratio("19945", "12345")
60

I understand the simple ratio is "matched chars"/"all chars", but how is #A showing 80% similarity? How are there 8 matching chars? thanks!