I like the sarcasm going on here !
What is the order you want? If the panels are in a linear array, yes, your description “0,1,2,…” is enough. (even though you would need to specify direction)
When we go 2d, well, there are already countless ways of numbering. By column? by rows?
The facade looks to be a 2d numbering problem, so we need a little bit more precision.
Maybe you can pull out a paint capture where you mark the numbering you have in mind?