Azure Search with vector (2024-05-01-preview) strange results varying k parameter value

what is the default value for k if it is not provided ?

when i do a query in the portal this value is not set .. and I get for a specific query a score equal to 0.03205128386616707
if i set k = 1 i get a score of
0.01666666753590107

if i set k = 5 i get a score of
0.01666666753590107

if i set k = 6 or above i get a score of
0.03205128386616707 (same as when k is not provided)

how is that ?

thanks enrico