In a certain code language, PETAL is coded as 11-22-7-26-15. How will UNDER be coded in that language?

Let's check the letters of PETAL against their reverse numerical positions (where Z = 1, Y = 2, ..., A = 26), or using $(\text{Position}=27-\text{Forward Position})$:P $\to 27-16=11$ E $\to 27-5=22$ T $\to 27-20=7$ A $\to 27-1=26$ L $\to 27-12=15$ This matches the code 11-22-7-26-15.Applying the exact same positional rule to UNDER:U $\to 27-21=6$ N $\to 27-14=13$ D $\to 27-4=23$ E $\to 27-5=22$ R $\to 27-18=9$ The code for UNDER is 6-13-23-22-9.