Those offsets are not contiguous... So, it seems like this tool is finding remnants of Berkeley DB files scattered across the disk image.
Also, note that just because it is a Berkeley DB file, doesn't mean that it's a wallet.dat file. There are other applications that also utilise this DB format.
Extracting a "big blob" should be relatively easy with dd:
dd if=input_file of=bigblob.bin skip=$start_offset count=$(($end_offset-$start_offset)) iflag=skip_bytes,count_bytes
In your case, you probably want $start_offset to be smaller than the lowest offset that the output shows... (ie. from your post: 18447876096)... and the $end_offset should greater than the highest offset + 4kb block size (ie. from your post: 19158560768 + 4096 = 19,158,564,864), so you can be sure that you're including all the fragments.
Actual Start = 18447876096
Actual End = 19158564864
Round the start offset down and the end offset up to nearest 10k (or 100k or whatever)...
Start = 18447870000
End = 19158570000
Count = 19158570000 - 18447870000 = 710700000
So... the end command (using values from your post) would be something like:
dd if=/media/sda3/hdd.img of=bigblob.bin skip=18447870000 count=710700000 iflag=skip_bytes,count_bytes
Of course, you'll need to adjust the start/end as per the actual output values from your full findbtc log.
I know your next question after you do this is going to be "what do I do with the 'big blog'?"... and I've honestly no idea. As the author of this app pointed out, this utility doesn't piece anything together, so you're going to need to do a bunch of "forensic" level work to be able to extract this data and then piece it all together... or try to find a trustworthy service to do it for you.
You would need to try and read all the individual chunks of Berkeley DB and try to piece them back together to try and rebuild the DB file... and then hope that you have enough of it to be able to extract the key data.
Honestly, if you're not trying to recover a very large sum of BTC, you might find that the costs involved outweigh the reward
ye that worked i scanned the hdd and during the scan it shows me possible wallet.dat traces block offset bytes but when the scan is completed 100% i get this ,
[scan] Starting new target: Gzipfile @ byte 192377703233 in [/media/sda3/hdd.img]
[scan] Unable to scan target: flate: corrupt input before offset 27
...
Those errors mean that a potential gzip file was too corrupt to be able to be decompressed and read. If your wallet.dat was in one of those gzip files, you likely won't be able to recover it.