The 4 unique guests for a typical zoo are man, woman, boy, and girl. So LouisXVI_garden.zoo has all 4 types of guests. Numbers are not used to determine uniqueness. So if Guest 1 and Guest 2 are both women, that counts as 2 total guests, but 1 unique guest. Almost all zoos will have up to 4 unique guests, but a zoo can have more. For example, the animals as guests hack can have up to 48 unique guests in the zoo, being that it uses different animals as zoo guests. But that hack was meant just for brief fun rather than as something that is used often. I do not remember if ZT allows renaming a guest. If so, that would also be a unique guest.
The 6 unique staff for LouisXVI_garden.zoo are male zookeeper, female zookeeper, male maintenance worker, female maintenance worker, male tour guide, and female tour guide. Other zoos might also have male and female scientists, male and female marine specialists, and the DRT helicopter. The staff can be renamed in ZT, which also can make each one unique. The ZKL Zoo, for example, has the staff with names that match their assigned exhibits. So that zoo has 87 total staff and 57 unique staff.
The Zoo Object List program for LouisXVI_garden.zoo gives counts for each unique guest and unique staff. It shows:
Number of guests currently in zoo: 253 total, 4 unique
Highest guest number currently in zoo: guest 667
Number of staff: 10 total, 6 unique
...
58 guests:boy: Guest
69 guests:girl: Guest
60 guests:man: Guest
66 guests:woman: Guest
3 keeper:keeper:f: Zookeeper
1 keeper:keeper:m: Zookeeper
1 maint:maint:f: Maintenance Worker
2 maint:maint:m: Maintenance Worker
...
1 tour:tour:f: Tour Guide
2 tour:tour:m: Tour Guide
So the zoo has 58 boy guests, 69 girl guests, 60 man guests, 66 woman guests, 3 female zookeepers, 1 male zookeeper, 1 female maintenance worker, 2 male maintenance workers, 1 female tour guide, and 2 male tour guides. Those give 253 total guests, 4 unique guests, 10 total staff, and 6 unique staff.