As noelex mentions, Ronin's numbers don't account for the resistor that "twelve volt" LEDs already have in their package. Usually invisible or inscrutiable, so measuring with an ohmmeter is the simplest way to figure it out.
But then still, as said, no way to tell what power that has been designed for. A lot of cheap
"automotive" LEDs are designed to run BRIGHT and if they do they by allowing high power...no one cares, they were bright and cheap
. An assortment of resistors, or buying
a pack of 50-ohm or 100-ohm resistors and experimenting, may be the simplest solution.
Santa, if you're not familiar with resistors, you'd disconnect either side of one LED and insert one resistor at the break, see how that affects dimming it. Still too bright? OK, use two resistors IN SERIES, daisy-chained, so theri resistance adds up. Still too bright? Use three, etc. 50-75-100 ohm, any of those will give you some assortments to narrow it down with.
I've got a vague memory, from "once upon a time I bought one of those" that the resistor in the "12 volt" LED is about 330 ohms, and you might need to crank that up to 1000 ohms to get it down to 10mA and night-time friendly. Which might also make it impossible to see in daylight. So maybe experimenting with 100-ohm resistors is a good way to start.