1 gram of Iodine has 0.007879943078443178 Iodine moles,
Like Borek: said, you can't weigh anything out to 10 decimal places, so you can just chop them off, at a point where you can measure. Or, you can just stop typing wherever. It's all cool.
Do you think you could help me out by explaining how the equation works relating to moles and ratios?
Sure. The units of a chemical formula are moles. Nobody, (mostly*,) picks up 3 diatomic iodine molecules, goes to the shelf and takes 2 phosphorus atoms out of the jar, and stirs it together with the 6 molecules of water.
What you want to do is start with the moles, from your reaction, and convert that to grams. Gram you can measure, that is, to determine what you need for the reaction to go forward.
*Work continues in chemistry on the visualization and analysis of single trapped atoms, but that is far outside O.P.'s application.