The number of elements in a control array is determined by the Index property for that object. This property will not exist for objects unless in a control array. The maximum value for index is 32767 (2^16 minus 1), including the zero(th) element this makes 32768 (2^16) elements for a control array.
Although in adding controls to a control array will automatically provide a successive list of index values for these objects (0,1,2,3,4....) this property can be set by the developer manually for each object, this can be useful if some controls are in the incorrect order, visually.
All the Best.