We have a minimum limit of 0.4 BTC for sell ads. This is unfortunatly necessary to avoid spam ads, we are very sorry for any inconvenience this might cause. We are looking into pegging this minimum to a fiat value in the future in order to react to price swings in a timely manner.
If you have less than the minimum amount you can always contact a buyer with a running buy ad.
Also please note that you need to leave 1% above the sum you want to sell for the localbitcoins.com sales fee.