Define returning type as packed number for method

I am learning ABAP Objects. I'd like to have an object method returning packed number type. I've made that working finally, but I don't know if it is the correct way and I'd need some further explanation which I can't find online.

For integer, it works fine:

METHODS: getamount RETURNING VALUE(r) TYPE i,

For packed number it doesn't:

METHODS: getamount RETURNING VALUE(r) TYPE p,

Error: The type of RETURNING parameter must be fully specified

METHODS: getamount RETURNING VALUE(r) TYPE p LENGTH 10 DECIMALS 3,

Error: The type of RETURNING parameter must be fully specified

(1) Is there way to make it work with p type?

I made it work by using dec5_2:

getamount RETURNING VALUE(r) TYPE dec5_2

(2) Is it the correct alternative? Is there a list of similar types?

Also, I found this solution, but it doesn't work for me:

CLASS lcl_rowinvoice DEFINITION.
  PUBLIC SECTION.
    METHODS:
      getamount RETURNING VALUE(r) TYPE typeprice,  
  PRIVATE SECTION.
    TYPES:
      typeprice TYPE p LENGTH 10 DECIMALS 2,

Unknown type "TYPEPRICE".

(3) Is there way to make this solution to work?

Returning parameters have to be fully typed, p is a generic type, so you have three options:

1. Use a predefined data element from the Data Dictionary (SE11 => Data elements)

 METHODS getamount RETURNING value(r) TYPE netwr.

2. Use a type which is defined in the PUBLIC section of the local class

TYPES: lty_p TYPE p LENGTH 15 DECIMALS 2.
METHODS getamount RETURNING value(r) TYPE lty_p.

3. Use fully predefined type (decfloat16 or decfloat34)

METHODS getamount RETURNING value(r) TYPE decfloat16.