see https://www.zabbix.com/documentation/3.0/manual/config/items/itemtypes/internal
for the zabbix[wcache,<cache>,<mode>] item key, it talks about values for float, uint and str modes, but then reverts to "items" for log and text modes.

that seems suspicious, as it would be expected that those are still values for these types, not item count (as would be the case with unsupported items).

another thing worth clarifying - most likely, unsupported items are actually attempts that result in items becoming unsupported or keeping that state - in that case it could be rewritten as "number of times item processing resulted in it becoming unsupported or keeping that state" - or a better version of that