I see in the chart it says Multiple Entries, 12 months validity is available. For US passports, what is the maximum stay *per* entry? 30/60/90/duration of visa?

I see in the chart it says Multiple Entries, 12 months validity is available. For US passports, what is the maximum stay *per* entry? 30/60/90/duration of visa? L type just as flexible? Or F necessary? If F, what are requirements for F over L? Absolutely no intention of doing business. In past 18 months have had a history of multiple visas and multiple entries, both L and F. Thanks.