My Words list is really weird
I'm French, learning on Duolingo since mid December 2016. I focus especially on English for French and practice a lot, so that I'm on the way to reach level 16. But my list of English words is blocked at 1270 since weeks. I'm using both User Interfaces: Web on Windows and the Android app.
Today I began and finished the opposite side in about 2 hours, learning French for English. I used every "test out" shortcuts available, doing the 64 first items in one single step and then the 13 others. I was using the Android app and now I'm training to reach level 12 using the "threngthen skills" button on the Web interface with Firefox and Windows. It lets me select the timed training feature the Android apps doesn't have.
Now, looking at my list of French Words I learned today, the count is 895 and it continues to grow, but when I look inside, I see in it many words that I'm sure I've never learned (carotte, haricots, insecte..) and lot of other one that are missing. For instance, I've "bought" the optional lesson "Idioms" to activate the hability to test the "Christmas Bonus Skill" I used the shortcut to pass it and in my list I'm supposed to having learned only two new words: "père noël" & "pôle nord", and no "rennes", "traineau", "guirlande", "décoration" aso...
I will continue to look at how those lists behave. I already submitted a bug report, but it's a message in a bottle, one doesn't know if someone cares of it. So posting here gives me a chance to see how it works for others and maybe to find a workaround, so that DL could stop asking me over and over to translate "chocolat", word that I did never fail to translate and that appears every day now and about one time every two lessons. :-(
I'm not complaining, just reporting.
Hopefully one of the moderators can answer your question fully.
My personal experience is that I started with the French tree (from English) and reached level 16. My word count is 1,284 having completed that tree. When strengthening the tree I learnt just a few more words. I tested-out the majority of the modules and words are added as you reach the higher levels (max. level 25).
The English tree from French (reverse tree) have many words new words which I do not learn from the first tree. I have not tested out any modules because I am gaining more practice of writing sentences in French. As a native English speaker, the reverse tree has been more useful.
I think that the word count varies widely depending on how many modules are tested out and the overall level reached: