As Brad points out, only grain (fermentables) are part of color calculations. Fermentables have to be expressed as a ratio of Lb/Gal or Kg/L.
Sinamar is a trademarked product of Weyermann and is 100% Carafa extract. According to their website, it has a starting color range of 3040 to 3200 Lovibond and an extract gravity of 55 Brix. What we have to do is convert those numbers into the ratio needed by BeerSmith.
Weyermann gives us two ways to approach the color. First is the color range of 3040 to 3200. The second is their instructions, which is 1.5 oz by weight (1.25 fluid oz) gives a barrel (31 gallons) 1* lovibond. Note the difference between the weight and volume measurements!
A gallon of water weighs 8.33 lbs.
From the color range:
3040 / 8.33 = 370
3200 / 8.33 = 384
From the instructions we first convert the weight dosage into lbs per barrel, then per gallon:
16 / 1.5 = 10.66 for 1 lbs conversion.
1.5 * 10.66 = 16 lovibond in 31 gallons
16 * 31 = 496
From 370 to 496 lovibond is quite a large range. An addition of 4 fluid ounces in 5 gallons would contribute ~15 to ~20 lovibond. That's enough to push gold into copper and copper into brown. I use the 384 lovibond color for my calculations and can reliably predict color with it.
The weight of Sinamar brings a specific gravity issue. At 53 brix, it's a light syrup. Again, we turn this into a lb/gal ratio. Brix is already an expression of weight, so we just convert that to specific gravity and divide it into a gallon of water.
53 brix = 1.250, aka 250 gravity points.
250 / 8.33 = 1.030
Sinamar then offers these specs for BeerSmith:
Type: Extract
Max: 10%
Color: 384
Potential 1.030