Only the positive converter is stabilezed. The negative reaches maximal - 5.4V because it's a little Transformer , the diode gets at least 0.6V. By increasing load the negative Converter loses about 70mV for 10mA of consumers load. It's very good for positiv Conversion, very stable and independend from load. A trick if you can sold with SMD: this cicurit is documented in the pdf of the chip XL6007E1. By reducing the 2K restistance with 47K to about 1,9K you manipulate the positive conversion to 6.4V, The very stable positive conversion you can easly reduce to 5.8V with a diode after this. By this trick you can regulate the negative deficit how is needed. The positive conversion is about 95%, neagtiv about 75%, that's very good. The consumption without load is about 5V and 3-4mA. It's good by using tricks, but the properties in description are not correct.
Everything was OK, I recommend this seller and give deserved five stars. Shipment to Poland took about 3 weeks.