Explanation:

In the given codes SURPRISE and TWUIKGUK:

S and T have 0 letters in between so O will be written as P.

U and W have a plus 1 letter, so P will be R.

R and U have plus 2 letters, so P will be S.

P and I have negative 6 letters, so O will be H.

R and K have negative 6 letters, so S will be N.

I and G have a negative 1 letter, so I will be G.

S and U have a plus 1 letter. so T will be V.

E and K have plus 5 letters, so E will be K.

Plus 1 plus 2 letters means the succeeding letters, which comes after.
Negative letters means the previous letters, which comes before.
Hence, the final answer will be PRSHNGVK.