Simplify the following text for a Grade 12 native English-speaking person.
Original: In addition , the Young Plan divided the annual payment , set at two billion Gold Marks , US$ 473 million , into two components , one unconditional part equal to one third of the sum and a postponable part for the remaining two-thirds .
Simplified: In addition , the Young Plan divided the yearly payment , set at two billion gold marks ( US$ 473 million ) , into two parts : one part equal to one third of the sum and could not be postponed and a postponable part for the remaining two-thirds .