Question about 5.4.3 safety argument

[zhiwen huang]

  Hi guys, I've been reading the masterpiece for several weeks while struggling with one question which maybe easy for you.

One paragraph in 5.4.3 safety argument says:

  

    7. Otherwise, leaderU’s last log term must have been larger than the voter’s. Moreover, it was larger than T, since the voter’s last log term was at least T (it contains the committed entry from term T). The earlier leader that created leaderU’s last log entry must have contained the committed entry in its log (by assumption). Then, by the Log Matching Property, leaderU’s log must also contain the committed entry, which is a contradiction  

Appreciate it if you can explain what the bold text means!