TDS level of purified water at the outlet of Aqua Guard I- Nova is 447. Is it ok ? or we have to use RO?

What is the purpose of using Aqua Guard ? TDS level of purified water at the outlet of Aqua Guard I- Nova is found 447. Is it ok for health ? or we have to use RO purifier. If we use RO purifier of Propello in place of Aquaguard , can that be ok? Why UV technology unable to reduce TDS?