Is it possible to detect specific child node that changed?

Hello :slight_smile:

 ㄴ3232390293(thes is uid)
    ㄴ point 
       ㄴ value1 : 500
       ㄴ value2 : 1000

above is my firebase database.

when value1 is changed to 700,
I want to detect in ionic app that value 1 is changed !

  //this.uid = 3232390293
 var a=this.afDb.list<Item>("/storeList/"+this.uid+"/point").valueChanges()
  a.subscribe((snap)=>{ => {
  this.firedata.child(this.uid).child("point").on('value', (snap)=> {
      console.log(snap.val()+"value changed!"+snap.key);
      for(var result in snap.val()){

but above code log is called whatever is changed under point node.
How can I detect only value that is changed?