Enter the component of the force on the lifting lug/trunnion, perpendicular to the wall of the vessel. This load will cause an axial stress on a perpendicular lug and a bending stress on a flat lug.
CodeCalc assumes that the magnitude of the applied loads is acting on one lug or one trunnion. Typically vessels are lifted with 2 ( or more ) lifting lugs/trunnion, thus the load is divided between them. An option is to analyze the lug/trunnion with the maximum load, acting on that lug/trunnion, during the whole lift.
The program multiplies this lifting load by the importance factor that you specify. For the horizontal lift position, this load will include part of the weight of the vessel.