Question: How much memory leak is negligible? 

In my program, I am using `Unity` and when I go through `Profile` > `Leaks` and work with the project it shows about total 16KB memory Leak caused by `Unity` and I cannot help that.

EDIT: After a long play with the program it amounts to a 400KB leak. 

What should I do? Is this amount of memory leak acceptable for an iPad project?

Answer: 
It's not great, but it won't get your app rejected unless it causes a crash in front of a reviewer. The size is less important than how often it occurs. If it only occurs once every time the app is run, that's not a big deal. If it happens every time the user does something, then that's more of a problem.

It's probably a good idea for you to track down these bugs and fix them, because Objective C memory management is quite different compared to Java, and it's good to get some practice in with smaller stuff before you're stuck trying to debug a huge problem with a deadline looming.
First, look if you can use Unity in another way to circumvent the leak (if you have enough insight into the workings of this framework).  

Then, report the leakage to the Unity developers if not already done (by you or someone else).  

Third, if you absolutely rely on this framework, hope it get fixed ASAP, unless switching to another framework is an option for you.  

A 400K leak is not a very big deal unless it amounts to that size within few minutes. **Though, no matter how small the leak, it is always necessary to keep an eye on any leak caused by your or third party code and try to get rid of them in the next minor or major iteration of your app.**