A very important doubt in DP about Recurrence relations

https://codeforces.com/contest/505/problem/C
This is the question. Can you please help me find the recurrence relation? If you will read the editorial you will find that they have used relation:
dp [ i ][ j ] = (the number of the gems on island i ) +
max( dp [ i + j - 1][ j - 1], dp [i + j ][ j ], dp [ i + j + 1][ j + 1]),
if i < m , j ≥ 2
but in recurrence relation we used to find out the previous state on (right hand side of the equation because that is how we solve sub-problems ) but here they have related dp[i][j] with the state that will be achieved afterwards that is dp[i+j+1][j+1], dp[i+j][j] and dp[i+j-1][j-1]. How are we solving sub-problems here? Can you please help me?