To calculate the density, divide the mass by the volume.
350/95 = 3.684 gm/cc (rounded)
The candlestick has a density of about 8.95 g/cm3
Divide the mass of the object by it's volume in your question 350 g / 95 cm3 to find density. Your answer will be 3.7 g cm-3 ( grams per cubic centimeter).
There are several possible reasons:Inaccuracy in measurement in the smaller amounts could give rise to a combined apparent error in the larger amountSome trace amounts of fluid may be left behind in the beakers that were used to measure the fluidIf the two fluids are not the same temperature, there could by a small amount of thermal expansion/contraction when the fluids are mixedSome fluid could be lost to evaporation, especially true of alcohol