Why does umi add an extra characters to the beginning of the meta data?

 const umi = createUmi(rpcUrl); umi.use(mplTokenMetadata()); umi.use(signerIdentity(source)); const memo = {     memo: '1' } let transaction = await transactionBuilder()     .add(addMemo(umi, memo))     .add(createNft(umi, {...}))     .setFeePayer(source)     .buildWithLatestBlockhash(umi);

After signing this transaction I noticed that extra characters were added to the beginning of the memo data.

Why were they added and is there a way to prevent them from appearing in the memo data?