I normally ignore row zero in my levels array
My 100 level array is 100,5,1
Basically just X,Y no Z
key - val1, val2, val3, val4, val5
You could do 50,6,1
Key - lvl1, score1, lvl2, score2, lvl3, score3
OR
Key - lvl1, lvl2, LVL4, score1, score2 score3
++++++++++++++++++++++++++++++++++++
Example
Lookup scores of level 25
Array Layout = Key - lvl1, score1, lvl2, score2, lvl3, score3
Key 25 - Level 1 and Score = 0,0 and 0,1
Key 25 - Level 2 and Score = 0,2 and 0,3
Key 25 - Level 3 and Score = 0,4 and 0,5
However, I would store the score separate from the Level array
Lookup Level array and then lookup Scores array to get values
If you put scores in the same array as the levels and then update the game (adding more levels) people could lose their progress