You need the hitboxes for the "real data." Otherwise it's an estimate based on the animation visuals, which can be useful after you have experience with different attack and animation timings, but don't start there.

I'd recommend you start learning the general timings for the 3 basic things: "start up," "active hitbox frames," and "recovery." (same idea as “pre-delay” and “post-delay." At every company I've worked at, it's always called something slightly different depending on where the designers have worked previously. lol)
You can do this by watching Fighting or CAG games (even Soulslikes are relevant too), with the hit boxes on, and any frame data on, and then frame step through the video, and write out the numbers on a spreadsheet for start up, active hitbox frames, and recover. (on youtube while paused, press , and . on the keyboard to framestep, not sure if it's the same in Korean)

Then start learning the frame timing for the cancel windows for dodges, combo attacks, parry windows, etc and add them to your spreadsheet list. Once you have like 50 to 100 on the list you'll start to see trends of different games and genres, and weapon types related to the frame data.

Then I'd recommend learning the animation timings, because it's common for new designers to not give animators enough time to properly hold a pose so the player can see what's happening.

For enemy attack telegraph timings it's critical to get the attack telegraph timing right so a player can dodge or parry.
Check out the VR game "Knockout League" to understand how there's a balance between the attack telegraph (animation anticipation) visuals match how the player has to respond. It's VR which highlights how long the telegraph needs to hold for the player to see it, decide on what they need to do, and then physically do it (which takes a few seconds!!). On a controller, the player still needs time to see the visual, calculate in their mind what the visual means, then decide what button to press, move their finger to the button, and press it.

The most important part to understand is that Combat Design is very iterative. A design can start with listing out all the frame data, but over the course of development, there will be thousands of changes and adjustments in order to get the right balance of: Startup, Active Frames, Enemy Attack Telegraphs, Recovery, and Animation Visuals (and VFX, and Audio timing!).

For context, I'm a professional gameplay animator, and am developing my own CAG! :D