aphexbganswered grow question 4 years ago I've got the same light, you can go a bit closer than what directions (Seedling: 76,2cm Germination: 60cm-76cm Veg: 45cm-60cm Flower: 30cm-45cm).
For flower I went as close as 20cm, but closer than that caused light burn, so I had to back it off a bit. I have 60x60 tent with 2 plants in my case, but i'm struggling with the room.
Good luck, hope this helps you plan better!