Exact meaning of TCH in X$BH

the official definition is : "|X$BH.TCH| is a touch count for the buffer. A high value for |X$BH.TCH| indicates a hot block." (Source:
https://docs.oracle.com/en/database/oracle/oracle-database/19/tgdba/instance-tuning-using-performance-views.html#GUID-64F78817-8B4C-4392-B518-CA31CF728B69).

But the biggest value for tch I have ever seen is 255 (unsigned seven bit integer) . Therefore I think it is not exactly a counter but rather reflects a range.
Can somebody give a detailed explanation? Does the number wrap around? When?

Thanks

Lothar

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