One of the rebuilders of the RV refrigerator coils sent a chart to go by that shows what the box should be with it properly leveled, door sealed, operating unit based on ambient temperatures. Here is the list he sent me. My unit runs close to these numbers over the limited range I've tested it.
Ambient Box
72 22
73 22
74 23
75 23
76 24
77 24
78 25
79 26
80 26
81 27
82 27
83 28
84 28
85 29
86 30
87 30
88 31
89 31
90 32
91 33
92 33
93 34
94 35
95 36
96 37
97 38
98 39
99 40
100 41
101 42
102 43
103 44
104 45
105 46
106 47
107 48
108 49
109 50
110 51
111 52
112 53
113 54
114 55
115 56
Hope this helps!