Vue.js - Input, v-model and computed property

Reading this vuejs, will understand what happens

"computed properties are cached based on their dependencies. A computed property will only re-evaluate when some of its dependencies have changed."

Changed some comportament of the code. Made run: computed() method not works properly for update value in window. But if looks at console the value yes updated. So, i remove computed (getter and setter), and put into data, without setter and getter( i dont like this in javascript).

var Main = {
  data() {
    return {
      measurementValueDisplay:'fff',
      enteredValue: '',
      max: 50,
      min: 10
    }
  },
  computed: {
      /*measurementValueDisplay: {
          get: function () {
              console.log('Computed was triggered so I assume enteredValue changed',this.enteredValue);
              return this.enteredValue + ' inchs'
          },
          set: function (newValue) {
          console.log('setter de qye', this.enteredValue);
          }
      },*/
  },
  methods: {
      formatInput($event) {
          this.enteredValue = 0;
          
          let inputValue = $event.currentTarget.value;
          console.log(inputValue);
          if (inputValue > this.max) { this.enteredValue = this.max}
          else if (inputValue < this.min) { this.enteredValue = this.min}
          else this.enteredValue = inputValue
          this.measurementValueDisplay = this.enteredValue + ' inchs'
          
          console.log(this.enteredValue, 'oioioioio0');
      }
   }
}
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

In case anybody still needs a hack for this one, you can use a value that will always change ( for example a timestamp )

var Main = {
  data() {
    return {
      enteredValue: '',
      max: 50,
      min: 10,
      now: 1 //line added
    }
  },
  computed: {
      measurementValueDisplay: {
          get: function () {
              return (this.now - this.now + 1 ) * this.enteredValue + ' inchs'; //line changed
          },
          set: function (newValue) {
              this.now = Date.now(); //line added
          }
     },
  },
  methods: {
      formatInput($event) {
         let inputValue = $event.currentTarget.value;
         if (inputValue > this.max) { this.enteredValue = this.max}
         else if (inputValue < this.min) { this.enteredValue = this.min}
         else this.enteredValue = inputValue
      }
  }
}

Your problem is that the values used in the computed property was not updated with the validation capping at 50 (Was 50, is now updated to 50, no need to recalculate), therefore v-model did not update the input.

I've edited your jsfiddle to use two computed properties:
One with an accessor to validate the entered value, one which returns the value with " inch" appended.

Here is the interesting part:

    computed: {
          measurementValueDisplay: {
              get: function () {
                  return this.enteredValue
              },
              set: function (newValue) {
                 this.enteredValue = 0;
                 let inputValue = parseInt(newValue);
                 if(Number.isNaN(inputValue)){this.enteredValue = this.min}
                 else if (inputValue > this.max) { this.enteredValue = this.max}
                 else if (inputValue < this.min) { this.enteredValue = this.min}
                 else this.enteredValue = inputValue
              }
         },
         valueWithInch(){
            return this.enteredValue + " inch";
             }
      },