Check out example codes for "angular number pipe". It will help you in understanding the concepts better.

Code Example 1

//{{ value_expression | number [ : digitsInfo [ : locale ] ] }}

//Assume someNumber = 12.221
	<!--output '12'-->
	<p>{{ someNumber | number : '1.0-0'}}</p>

//The output here is '12' because we cut the decimals off
//with the number pipe

//More examples from Angular:

	//Assume:
    //pi: number = 3.14;
  	//e: number = 2.718281828459045;

	<!--output '2.718'-->
    <p>e (no formatting): {{e | number}}</p>

    <!--output '002.71828'-->
    <p>e (3.1-5): {{e | number:'3.1-5'}}</p>

    <!--output '0,002.71828'-->
    <p>e (4.5-5): {{e | number:'4.5-5'}}</p>

    <!--output '0 002,71828'-->
    <p>e (french): {{e | number:'4.5-5':'fr'}}</p>

    <!--output '3.14'-->
    <p>pi (no formatting): {{pi | number}}</p>

    <!--output '003.14'-->
    <p>pi (3.1-5): {{pi | number:'3.1-5'}}</p>

    <!--output '003.14000'-->
    <p>pi (3.5-5): {{pi | number:'3.5-5'}}</p>

    <!--output '-3' / unlike '-2' by Math.round()-->
    <p>-2.5 (1.0-0): {{-2.5 | number:'1.0-0'}}</p>

//More information here: https://angular.io/api/common/DecimalPipe

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