1/8 means 1 bucket used out of 8 allocated.

for (0..15) {
    $a{'a'}{$_} = 0;
    print scalar %{$a{'a'}}, "\n";
}
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And the output is -

1/8
2/8
3/8
3/8
3/8
4/8
5/8
6/8
8/16
9/16
10/16
11/16
11/16
11/16
12/16
15/32
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If you want to find out the actual size, flatten into a list first.

print scalar @{[%{$a{'a'}}]}, "\n";
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