Always measure anchor depth from deck rather than waterline, your anchor is attached at deck level.
In tidal water, calculate depth at high tide.
Some sounders are set to display depth under keel, and you'll have to add the draft.
Put enough chain
Your anchor works well if it is pulled horizontally, to achieve that you need a chain length of 5 times the depth. With a 5 to 1 ratio, the angle of pull will not exceed 11.5° and the anchor will work correctly. Eg. with a depth from sea bottom to deck at high tide of 10', you need 50' of chain.
In rough conditions, good sailors add more chain !
Check the chain
Once the anchor is set, let the boat find its place downwind or down tide. Wait for the wind or tide to make the chain tensed, or put your engine in backward gear : the chain will straighten. Put your feet on the chain. If the chain trembles, the anchor drags.
Do not exceed a very gentle engine pull back. The pull back is sufficient if the chain gets tense.
If you need to pull more strongly to dig the anchor, do it after you set the chain hook.
Wear appropriate shoes and make sure no one is maneuvering the windlass
Preserve your windlass
Unlike your windlass, cleats are designed to take the load.
With engine in idle, put a chain hook on a suitable nylon and secure it to a bow cleat. Then give some more chain until the nylon is tight and the chain really loose.
When conditions requires to dig the anchor in, proceed safely with a stronger pull back.
Maintain the watch
You should check periodically your position relative to the circle in your alarm app and keep an eye outside as you were taught while learning sailing.
As a boat Master or Skipper, you are responsible to keep the crew and the boat safe. No electronic aid nor app will relieve you from your responsibility nor liability. Electronics aids and apps offer an aid but they might fail, be inaccurate, be unavailable... yet you're still in charge.