That looks like a sketchy denialist source to me. I don't trust it to accurately summarize scientific results.
The article it references is pretty clear on that: "The ice sheet also loses ice by the breaking off, or “calving”, of icebergs from its edge, but that is not included in this type of budget. As a result, the SMB will always be positive – that is, the ice sheet gains more snow than the ice it loses."