How does being good at typing affect your career positively?

Being good at typing can be an advantage for some careers, and it can improve your work because you are finishing more assignments with less time.

Typing is a skill of accuracy and speed and learning to do so is a good investment but it is not that important.
Improving your speed will not improve your productivity much but if you were writing a book then an accurate and controlled speed of typing can save the writer maybe an hour a day.
Typing is merely an understanding between you and your keyboard.
In my profession, typing has proved fruitful as I currently type in excess of110 words per minute.

Being good at typing is an advantage as a secretary.
It helps me improve my job, less time, more production (being efficient).

Typing (of course the right way) is a skill acquired through constant practice. 

This helps you to increase your mental alertness, focus and give attention to detail, increases concentration, helps you to read and type (2 actions at a time) at the same time (kind of multi-tasking skill) which is not acquired by everyone. 

This is a special quality of people who type.  Any job which requires the above qualities to perform it effectively will undersand the value of typing, since this is kind of a manual job (even though only fingers are involved), which increases efficiency and helps in time management as well.

Just concentrate on what you are typing and like wise your fingers moves faster....that makes you perfect

it affects my career hugely because I will be faster at accomplishing all tasks given to me

Being good at typing is an advantage as a secretary.
It helps me improve my job, less time, more production (being efficient).
It builds confidence on what I am doing as a secretary.
Most of all, it becomes my key to enter in different organization.