"Startup" means the start of an offset litho print run. There is always some waste at startup; it takes a little time for the flow of ink and the balance of ink and water in the various cylinders in the press to reach the optimum state, so the first sheets printed have to be discarded. This ink supposedly has properties that reduce this time, and the consequent waste.

"Printing presses are designed to print the same image page after page on a large number of pages [...] After some number of initial "startup" rotations of the cylinders, the ink flow off of the plate becomes equalized to the ink flow onto the plate, and similarly the ink flow off of the blanket (onto the paper) becomes equalized to the ink from onto the blanket. [...]
The initial sheets which come off of the press are carefully checked by the press operator for registration (i.e. alignment) of each color plane [...] The operator also waits until enough sheets have been printed to achieve ink/water balance and to achieve steady-state ink flow on each of the sets of inking rollers, and then checks the optical density of test patches to verify that the proper amount of ink is being printed."
http://www.imaging.org/site/IST/Resources/Imaging_Tutorials/...

I don't know enough about printing ink to be able to guess why a particular ink may achieve this "steady state" more quickly at startup, but that is apparently what this ink allegedly does.

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Note added at 2 hrs (2018-09-19 01:50:41 GMT)
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(I think the end of the first paragraph of the quotation should probably read: "the ink flow off of the blanket (onto the paper) becomes equalized to the ink FLOW onto the blanket".)

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Note added at 3 hrs (2018-09-19 02:14:49 GMT)
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Hi Mónica. It's not easy to think of a neat way of expressing it in Spanish (English is so economical), but for a marketing text I think that would work well, yes. A literal version would be pretty cumbersome: maybe something like "alcanza rápidamente las características adecuadas del color al inicio de la impresión/tirada", or something like that. I'm trying to think of a way of expressing it with "reduce al mínimo...", but I can't see how to continue.