Fasta sequences have different formattings, e.g.:
1:>header
2:NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
1:>header
2:NNNNNNNNNN
3:NNNNNNNNNN
Fixed column sizes contain hidden characters like "/n". These are counted as sequences characters while copy/pasting.