How can objectHandle in HGDIOBJ objectHandle [1] be a variable length array?

Question

I'm trying to understand why in HANDLETABLE struct objectHandle is an array of handles. As I understand, HGDIOBJ is a void pointer and therefore objectHandle is an array of void pointer with an element. But in the book Programming Windows 5th Edition, author said that the field is actually of variable length. How can it work? I think that objectHandle only have 1 element??