Answer:
This is because you failed to move the number from short-term memory to long-term memory.
Step-by-step explanation:
Short-term memory can only store a very limited amount of information for a very short period of time - between 20 and 30 seconds. If a person wishes to keep that information stored for longer, they will need to move it to long-term memory, which can hold unlimited amounts of information for an indefinite period of time. Repeating information to yourself several times, for instance, can help such information to move from short-term to long-term memory. There are also strategies you can use to remember the information for longer periods, such as association or breaking it down into chunks.