Slave SQL thread : Time

First of all, My SHOW SLAVE STATUS shows

Seconds_Behind_Master: 0

I can compare my slave with master, n see that replication is perfectly synchronized.

Now here comes the issue,

When I run SHOW PROCESSLIST, it shows,

+-----+-------------+-----------+------+---------+------------+-----------------------------------------------------------------------+------------------+
| Id  | User        | Host      | db   | Command | Time       | State                                                                 | Info             |
+-----+-------------+-----------+------+---------+------------+-----------------------------------------------------------------------+------------------+
| 591 | system user |           | NULL | Connect |      29542 | Waiting for master to send event                                      | NULL             | 
| 592 | system user |           | NULL | Connect | 4294966950 | Has read all relay log; waiting for the slave I/O thread to update it | NULL             | 

you can see the time < 29542 > and < 4294966950 >.

I read in MySQL documentation that in SLAVE SQL THREAD, " The value in the Time column can show how late the slave is compared to the master. "

My replication server is consuming too much memory without any load, is this the reason behind this ? How can I rectify it ?