Because the number in the T-register is replicated when the stack drops, this number can be used as a constant in arithmetic operations.
T c c <---New constant generation.
Z c c
Y c c <---Drops to interact with X-register.
X x cx
Keys: *
Fill the stack with a constant by keying it into the display and pressing ENTER three times. Key in your initial argument and perform the arithmetic operation. The stack will drop, a copy of the constant will "fall" into the Y-register, and a new copy of the constant will be generated in the T-register.