> so the 3-syllable credit card is rendered in Japanese as a 6-syllable kureditto ka-do.

There are actually 8 mora (the western concept of a syllable is different from the close but different equivalent in Japanese).

ku-re-ji-(pause)-to-ka-a-do

While mora include all the Japanese sound combinations which look like western syllables, they also include the classification of “double consonants” and “long vowels” as 2 mora. The Japanese post-vowel /N/ semi-vowel sound (as in “shiMbuN”) is also a mora.