In the Soviet Union, the primary and dominant language was Russian. As you may know, Russian has no articles, while an average Russian word is 6.36 characters long.
In the early 1920’s industry a new industry standard called “author’s list” was created. It consisted of an unbelievable 40 000 signs (including spaces, numbers, and punctuation). Unlike Western standards in the Soviet Union, manuscripts were submitted with dual spacing. An average typewritten page was 1800 characters long (paradox, but 300 words in Western printing standard although average Russian word equals 1.24 English words). And if printed on a PC using a 12 point Times Roman with single spacing, an average page in Russian is 3500 signs big (584 Western words).
After the Soviet Union collapsed, people still widely used the word count standards in the former republics, as well as plenty of other standards. So if you get payment for units of 250 or 300 words, your client is most probably in Western Europe or America. But if your work has a limit of 1800 or 3500 signs, I bet that you got an order somewhere from the Community of Independent States.
Still, I have to explore the word count specifics in oriental languages. Soon an article on this topic will follow.
PS You can easily count word statistics almost in any document format using a word count software.