How to explain the case that the value of "Library Cache Hit Ratio" in V$METRICNAME is larger than 1

When I query the Library Cache Hit Ratio using view v$metric_history, the result is larger than 100%.

SQL> select sum(a.value)/count(*) pct from v$metric_history a where a.metric_name = 'Library Cache Hit Ratio' and group_id = 2 and a.begin_time >= sysdate - 1 and a.end_time < sysdate;

       PCT

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100.153536

How to explain it?