In general, you would take your total maintenance and multiply it by the deductable percentage . . . BUT, since the deductable percentage shown in most listings is an estimate, the accurate answer is to have your agent call the management company to get the true deductable $ per share and multiply that number by the number of shares that you own.
Mathematicaly one would multiple the fee by .55 to arrive at 55% of the fee. However beyond that a realtor is not licensed to and in many states if forbidden from giving legal or tax advice. If you have a question about deductibility I would call a good accountant and ask the question. I'm sorry that I couldn't be more help but this is an area where real estate agents shouldn't be handing out advice.