Custom Caching Limits for OS X Server
Your options aren't limited to the numbers printed below the scroll bar. You can drag between the options to select a value closer to your desired value:





You can set custom values if you really want to though. The cache size is stored in the CacheLimit key in the configuration plist which is located by default here:

/Library/Server/Caching/Config/Config.plist




&lt;key&gt;CacheLimit&lt;/key&gt;
&lt;real&gt;268586281855&lt;/real&gt;


The integer is bytes.