Can't reproduce:

my $nfc_amt = 115;
print "NFC_AMT before adding zeroes: $nfc_amt\n";
$nfc_amt = sprintf("%07d", $nfc_amt);
print "NFC_AMT after adding zeroes: $nfc_amt\n";
__END__
NFC_AMT before adding zeroes: 115
NFC_AMT after adding zeroes: 0000115
[download]

Likely it doesn't contain what you think it contains. Could you add this to your code and show us the output: use Devel::Peek; Dump($nfc_amt);