Hey @NachJo, it happens! Luckily, we have a couple of options that may work for you here.
If nothing has been done with any of the parts since receipt (i.e. they aren’t picked to an order yet) then you could cancel the receipt, the re-receive and assign the serials as normal.
If that won’t work, then you can assign serials to each part. First you’ll need to create pieces from the bin by editing it and clicking “Create Pieces”. Then you should get taken to the Bin Piece/Serial List
for the bin, and you can assign each piece the appropriate serial number there.
Hope that helps! Let us know if you have any other questions about this.