SQL & PL/SQL

I am trying to learn more about precision can some one explain me in a plain english ...

I am table column with number(22) and another table with column with number(15,2)

if I reduce column data type from number(22) to number(15,2)

I have alter table schema.column add (new_table number(15,2))

update schema.column set new_table = table

alter table schema.column drop column table

alter table schema.column rename  new_table to table;

will this make any difference from number(22) to number(15,2)