There are three ways to change a todo item’s priority:
Raise the current item’s priority by one, exchanging its position in the list
with that of the item directly above it (todo-raise-item-priority).
Lower the current item’s priority by one, exchanging its position in the list
with that of the item directly below it (todo-lower-item-priority).
Prompt for a number and relocate the item to the corresponding
position in the list (todo-set-item-priority). For example,
entering 3 at the prompt makes the item the third in the
category, i.e., gives it third highest priority; all lower priority
items are pushed down by one. You can also pass the desired priority
as a numeric prefix argument, e.g., 3 # gives the item third
highest priority without prompting. (Prefix arguments have no effect
with r or l.) And you can type M-p and M-n in
the minibuffer to scroll through all priority numbers for the current
category. If you mistakenly choose the item’s current priority, you
will be prompted to choose a different priority.