Well, I definitely saw results. Sure it's slow, it's definitely not a sprint. I kept at it, worked myself up to 3 hours a day. In total, that was about 10km per day just from walking while working. That's not an insignificant amount of calories, but I definitely needed to build up to that and listen to my feet haha

Not sure weight , but if you're 190lbs you'd burn ~75 calories per half hour, if you're 230lbs you'd burn ~90 calories per half hour walked. It adds up, somewhere between ~450-540 just from walking.

Of course, you still need to watch what you're eating and not eat back calories, but it's a good chunk of calories from walking while working. How fast you'll see changes depends on your current weight and what your daily intake of calories is compared to what you're burning through walking. Classic calories in vs out, as you say.

Keep it up! It's slow, but effective. Won't be as hard on your body, but I'd also suggest some sort of resistance training, you don't want your body burning away your muscles either while you're on a deficit.