[COLOR=#f9d648]Operations training dummies have 5814 armor rating (not visible to you), which translates through our armor formula to about 35% DR. With your setup, you cut that armor rating down by 55%, effectively turning it into 2616 armor rating. [5814 * 0.45 = 2616] 2616 armor rating translates through our armor formula to 19.5% DR.
That's a little unintuitive... if I have 55% armor penetration then my first instinct would be that I'll reduce a target's DR by 55%, but in this instance the actual DR is only reduced by a bit over 40%. I'm assuming the training dummies have enough armor to push them up into the diminishing returns area of the DR formula and therefore the first chunk of armor they lose has less effect on their DR. It would probably be a good idea to make it clear that armor debuffs like this don't automatically translate into an equal DR reduction, and you should definitely publicize any armor or other defenses on training dummies since that's kind of important for DPS calculations.