Keg, -hr, 11 bytes
÷(¿|")(4)⅍(5)∑Z
Explained
÷(¿|")(4)⅍(5)∑Z
÷ # Split m into individual numbers
(¿|") # n times, shift the stack right
(4)⅍(5) # turn each character into a string
∑Z # sum stack and convert to integer. `-hr` prints it as integer
Keg, -hr, 11 bytes
÷(¿|")(4)⅍(5)∑Z
Explained
÷(¿|")(4)⅍(5)∑Z
÷ # Split m into individual numbers
(¿|") # n times, shift the stack right
(4)⅍(5) # turn each character into a string
∑Z # sum stack and convert to integer. `-hr` prints it as integer