Most accurate way to look at new snow

Hello, what is the most reliable way to look at new snow ? If I look at the forecast for my location the total of the forecasted snow equal let say 15 cm over 24 hrs , so they may say .3cm at 3 then 1.5 at 6 than .9 at 9 and so on and the total will be 15cm. Now if I use the new snow icon with the picker for the same period they say 17.5 or else, the number are never or rarely the same ... why is that ? what is the most accurate number, the one under the picker or the one described in 3 hrs segment in the forecast ? Thanks !!

The detail of snowfalls forecast is interesting for knowing the intensity of precipitation. But the cumulation of snowfalls does not give an accurate measure of snow depth because the snow layer compacts by itself. When you select the Snow depth layer the weather picker shows at same time the snow depth and the snow density.
So the Snow depth layer is theoretically more accurate than the total of snowfalls.https://community.windy.com/topic/10232/snowfallhistorymap
http://bit.ly/snowdepthforecastmap 
@idefix37 Ok I think I got it , since english isnt my first language let see if I really got it : The snowfall forecast is telling me in theory the intensity of the snow fall EG, 1 cm per 3 hrs or 0.6 per 3 hrs etc etc , am I right ?
Now if I use the picker with the NEW SNOW layer I'll get the approximative accumulation at the rate of 1mm of water for 1 cm of snw without taking into account the real density of the snow , am I right ?
Finally , the SNOW DEPTH is the most realistic amount of snow that we will get ? Am I right ?
Where I am not sure again is, if I look at the picker now for my location on Tuesday feb 18 it says, snow depth 42.8 cm according to the snow fall and the density of the snow determined by the model, so I am assuming that it is the total amount of snow and height we have received so far up to feb 18 this winter, am I right ?
so for 18 hrs on the same day we are supposed to get according the the forecast apprx 13.9 cm so if I started the day with the snow depth picker at 42.8 and if I add 13.9 , the snow depth would be 56.7 by the end of the day on tuesday, but since the density of the snow vary, the snow depth layer picker is giving me 51.4 , so in reality the amount of snow received would be ( 51.4  42.8) 8.6 cm instead of the 13.9 shown in the forecast, am I right ? .... ok I have an headache, what about you ? :) anyway thanks a million for your help Idefix

@Homer1959
You are right. But don’t try to make precise calculation, because snowfall and snow depth are just rough estimation made by weather models. The figures are quite inaccurate if you are close to the rainsnow limit and in particular if you consider a location in mountains. The models resolution in mountainous areas it too coarse to give precise snow figures at each altitude levels.
This is the reasons why I asked to Windy developers to forget the decimal precision for Snow depth. 43.8cm is ridiculous and 44cm would be enough precise.For example this morning the satellite picture over the Alps shows clearly the areas covered by snow:
Compare it with the Snow depth layer from ECMWF ....

@idefix37 Ok great thank you !!! There is always something to learn ...its a lot more complicated than The Weather Network but its more fun :)