Ionic 2 / 3: Number Input from Alert

I'm using Ionic 3.x on macOS.

I have the following issue:

I have an array containing a number and an array of names.

table: { number: number, names: string[] } = {
    number: 0,
    names: ['']
  };

I want to set the number of the array using an input for the user. I stumbled upon the AlertController.

I have written the following function thing to add a number:

addTable(){

    let prompt = this.alertCtrl.create({
      title: 'Add Table',
      subTitle: 'Enter the table number',
      inputs: [{
        name: 'tableNumber',
        placeholder: 'Number',
        type: 'number'
      }],
      buttons: [
        {
          text: 'Cancel'
        },
        {
          text: 'Add',
          handler: data => {
            //this.tables.push(data);
            this.table.number = data;
          }
        }
      ]
    });

    prompt.present();

  }

But this always sets table.number to object [object]. If I write it as this.table.number = +data; it has the value NaN. The push version also doesn't work.

How do I set table.number to a number that the user put in?