For each signature number we count the number of records (N) corresponding to this signature. 
For each non-zero N (first column) we publish the total number (T) of such signatures.

If N = 123 and T = 2000, this means that the total number of such records is N * T = 246000.

To find the total number of records in the library we need to find the sum 
\sum N_i * T_i
