Sixth day of cycling - dosing ammonia wrong?

Ok so I'm on day six of my cycling with 50lbs dry and 8 lbs of live rock from LFS. 90G tank with sump. I had a shrimp in for the last 6 days and took it out today as it was nothing but goo and there were no ammonia readings. I put in 10ML of ammonia at 3:30 p.m. on 08/25 to achieve 3 ppm (used other forum's calculator and complicated math formula so this is right.)



I come home now, 1:45 a.m. and test the water.



PH 8.1

SG - 1.026

Temp 77.2

Ammonia 2.0 ppm

Nitrite - 0

Nitrate - 0



Why am I a whole 1 ppm off on ammonia?