Hi, dlsweb. I get confused with those, too. The answer will depend on whether the multi-value checkbox list is in the same table or an external table.
If category list is in same table, use the category label for your 'where' in this manner, note the $ on either side:
If category list is in same table, use the category label for your 'where' in this manner, note the % on either side:
'where' => 'category = "%Winery%"',
If category list is in an external table, use the category record number. For example, if your Winery category recordn number was 5 in the external table, that would look like this:
'where' => 'category = "5"',
Let me know if that works.
~ Deborah