Record Collection, [ ] and the creation of new properties in objects

I’ve been stuck for a while and looked at the solution, and found the thing that was wrong is the exclusion of [ ] in one line that’s identical to another that was correct.

Can you explain the difference between:

collection[id][prop] = [value];
collection[id][prop] = value;

[value] is an array that contains the content of value variable

The other one is just assigning there the content of value variable