Haha I was wondering the same when I saw 1000 used in both [bitcoinj](https://github.com/bitcoinj/bitcoinj/blob/e397928ec3fdba977dea9a4b02e9e6b14d757f84/core/src/main/java/com/google/bitcoin/core/Wallet.java#L1967) and [electrum](https://github.com/spesmilo/electrum/blob/9543d2b5ec54ba6793fe09291bc5cb0593a3538a/lib/wallet.py#L1131) I can't find any official docs but if 1000 is what everybody uses, there's probably a good reason.