What hides between Shadow and Light?

[Sunspots]

While I know We need to figure out the numbers before the letters, I tried to put the two lines of letters against each other as with a one-time pad deciphering and this is my terrible results:

When I use the first line as the ciphertext and the second as the key, my result is something starting with "TWHHUD..." which is certainly not the beginning of a word so I stopped there.

Then I used the second line as the ciphertext and the first one as the key instead, the result is something starting with "XWVDQP..." which neither is any kind of word.