I will define my own blocks:

block 1:
1234

block 2:
01234

block 3:
001234

...

block n:
000...0001234
(n-1) 0's

therefore the first block has 4 digits
2nd has 5 digits
...
nth block has n+3 digits

after exactly nth block, the total number of digits would be:

(4+n+3)n/2

or (n^2+7n)/2

I will now find the number of complete blocks such that the # of digits does not exceed 2550:

(n^2+7n)/2<=2550

gives me:

n^2+7n<= 5100

n=69....

so when n=69

(n^2+7n)/2-2550>4

so the digit is probably a 0