deduct insurance for partial year rental

[Jeremy H.]

I am running into a problem finding this number.

Let's say my property converted from personal to rental in June.  I cancelled the regular home owner insurance around June, to purchased a new policy that is rental insurance (mostly, it's a fire insurance).

So there is 2 policies that needs to be pro-rated  (home owner,  and rental policy).    Do I just deduct the insurance for the rental period (June - end of year)?    I am just having trouble coming up with the pro-rated number, it's probably like $150 and I don't want to get audited having to proof the number. 

Am I better off not deducting anything in this field?

Or do I enter the total expense insurance (both policies pro-rate) and the IRS formula will proportion them based on # of days?