Yes, שנתי means annual. So, it's annual turnover, which is a financial/accounting term of trade, which may mean a few things referring to speed of flow of money or resources. In the UK, it usually refers to what in the US is called revenue - how much money a firm takes in during a period of time (e.g., annual turnover); but, in the US the term does not refer to this. Which one is meant here is hard to say, exactly.
Thanks for the translation from British to American English! In the US the term would never be used to refer to revenue. It could conceivably mean the number of employees who leave a business and have to be replaced each year, but unless you're a manager and are feeling very possessive about your staff, you would never say "MY annual turnover".
In other words, in American English this is basically a nonsense sentence.
Edit a year later: It's still gibberish in AE. The only meaning I can force into those words is that the apple pastry that I only have on my birthday (my annual turnover) is undersized.
Hah, the birthday pastry was exactly what came to mind for me after I tried to figure out the possible business meaning. I've been (and am currently) in businesses where there is high staff turnover. But I suppose literal translation of "high staff turnover" into Hebrew would not make any sense either. You would probably think of Moses and the Egyptian wizards.