Whatsapp .. two ticks but recipient has no internet connection?

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My friend says they have problems with their internet connection, that's why they don't reply for long amounts of time and they aren't seen online for that amount of time either. However, everytime I send a message on whatsapp to my friend, two ticks appear next to it and that indicates that the message has been received by their device and usually when someone does not have an internet connection only one tick appears. So does that mean they are lying or they actually do not have internet connection but the device is still receiving the message?