The trimming in the pic is perfect. You can clearly see the quick (the opaque bit of the nail (in the shape of a triangle), before the nail starts curling) is about 1 or 2 mm away from the edge

If the quick was cut, there'd be blood, and a very pissed cat

I've got tons of cat scratchers, the ones that are very tall, so the cat can get a full stretch, and have a wide base, so they don't fall over

And 2 of my 3 cats still need nail trimmings about every 3-4 weeks. Otherwise their nails get stuck on things, or they claw me to death by accident since their nails are so long, they don't fully retract

My dog's nails, I have the vet handle, because I cannot trim black nails without hitting the quick

Edit: here's a link to the scratching post I use and recommend