FG High, help for carbonation/bottling

My Recipe
4,5 Kg Ale Organic Bio Minch Malt from Ireland
0,5 Kg Viking Munich from Finland
0,5 Kg Viking Crystal 100 from Finland

Mash 75 minutes at 68 Celsius
        10  minutes  at 71 celsius
        10  minutes mash out at 78 celsius
Yeast Dry Safale 04

20 Liters  OG 1061  FG  1023

For a.m recipe Beer Smith shows Estimated FG 1018.
Addition of Yeast, shake of fermenter have not changed Final gravity.
Please help me for quantity of sugar indicated for carbonation.
My doubts related to calculation of sugar quantity are caused by high FG.
Thanks,

How long has your carboy been fermenting?  What was the batch size? Did you direct pitch the dry yeast or did you proof it before pitching?  What was your fermentation temperature (temp of carboy/beer, not room temp), if you have measured it?  Has the final gravity reading been consistent for several days?

Final gravity calculations are pretty iffy to begin with.  So much of your actual results depends upon the quality of the yeast pitched, rate of pitching (billions of cells/ml/degree Plato), and temperature profile of your fermentation.  S-04 has an attenuation of 72% to 75%.  Right now you are around 62% to 63% attenuation, so there may still be some more work going on.  If you have just tested it at 1.023, let it sit for a few more days and retest the gravity to make sure it has reached its end point.  It has been many years since I have used S-04, but I don't remember that yeast as being prone to stalling during fermentation.  One thing you can try is to raise the temperature a bit more to help speed along the yeast activity.  If you are at 19 C or 20 C, raise the temp up a couple of degrees to 21 C or 22 C.

For your carbonation, your recipe in BeerSmith has the sugar requirements for carbonating right in the recipe.  This calculation is based upon your recipe and bottling volume.  If you are unsure about it, there is also a separate carbonation tool which you can use in BeerSmith to figure out for the amount of net beer you are ending up with (fermenter volume - volume of trub) to bottle.  If you have truly reached a stable FG, then you should not worry about using these figures.

Sorry for my english.
Carboy fermenting 15 days. I have started yeast with water at 35 celsius for 15 minutes, mixed and pitch after 5 minutes. Temperature of carboy is 21 celsius (i have a probe into carboy). Yes, Final gravity is 1023 by 7 days. For 20 liters i have pitched 15 grams of dry yeast.
Today i have put carboy at 4 celsius. Apparent attenuation is low but i have not idea related to cause.
I hope that carbonation will be ok.
Thank you

I've had low attenuation with S-04 before. Quite often actually. Follow Oginme's advice and raise the temp just a bit and if there is no change in a couple of days go ahead and package it. It will still be good.

Thank you!!