Potentially stupid question about water

I've had my tank cycling for almost 2 weeks now, and as such, some water's evaporated and it should probably be topped up. When I bought the tank, the LFS told me that they sell RODI water that's already mixed to the right salinity, and it seemed much easier to buy it from them than to mix my own at home and invest in an RO unit, so I bought 100 litres. With the live rock and sand etc, the tank actually comes down to only holding 75 litres, so I have one container of water left over, but it's just been sat in a sealed plastic container (sold by the LFS so it's clean at least) for 2 weeks with no filtration or even circulation.



Is it going to be safe to add this to my tank now to top it up, or will it have stagnated or in some way gone bad and shouldn't be added to the tank water?