clarify mathematical expression

Author: 719media

README.markdown

@@ -88,7 +88,7 @@ session.save_path = "tcp://host1:6379?weight=1, tcp://host2:6379?weight=2&timeou
 
 `session.save_path` can have a simple `host:port` format too, but you need to provide the `tcp://` scheme if you want to use the parameters. The following parameters are available:
 
-* weight (integer): the weight of a host is used in comparison with the others in order to customize the session distribution on several hosts. If host A has twice the weight of host B, it will get twice the amount of sessions. In the example, *host1* stores 20% of all the sessions (1/(1+2+2)) while *host2* and *host3* each store 40% (2/1+2+2). The target host is determined once and for all at the start of the session, and doesn't change. The default weight is 1.
+* weight (integer): the weight of a host is used in comparison with the others in order to customize the session distribution on several hosts. If host A has twice the weight of host B, it will get twice the amount of sessions. In the example, *host1* stores 20% of all the sessions (1/(1+2+2)) while *host2* and *host3* each store 40% (2/(1+2+2)). The target host is determined once and for all at the start of the session, and doesn't change. The default weight is 1.
 * timeout (float): the connection timeout to a redis host, expressed in seconds. If the host is unreachable in that amount of time, the session storage will be unavailable for the client. The default timeout is very high (86400 seconds).
 * persistent (integer, should be 1 or 0): defines if a persistent connection should be used. **(experimental setting)**
 * prefix (string, defaults to "PHPREDIS_SESSION:"): used as a prefix to the Redis key in which the session is stored. The key is composed of the prefix followed by the session ID.