I'm a bit confused by the output of my minerd from cpuminer because my understanding is that there is a 3 minute block target time, but somehow I got 4 submitted hashes in less than a minute, and it appears that they were also within a single block. What does this mean?

[2014-04-26 12:57:31] Stratum detected new block
[2014-04-26 12:57:31] thread 1: 23304 hashes, 3.88 khash/s

[2014-04-26 12:57:47] thread 2: 62472 hashes, 3.89 khash/s
[2014-04-26 12:57:48] accepted: 406/1106 (36.71%), 31.11 khash/s (yay!!!)
[2014-04-26 12:58:24] thread 1: 205104 hashes, 3.90 khash/s
[2014-04-26 12:58:24] accepted: 407/1107 (36.77%), 31.13 khash/s (yay!!!)
[2014-04-26 12:58:25] thread 5: 211068 hashes, 3.91 khash/s
[2014-04-26 12:58:26] accepted: 408/1108 (36.82%), 31.14 khash/s (yay!!!)
[2014-04-26 12:58:28] thread 1: 16788 hashes, 3.95 khash/s
[2014-04-26 12:58:32] thread 7: 234624 hashes, 3.90 khash/s
[2014-04-26 12:58:34] accepted: 409/1109 (36.88%), 31.25 khash/s (yay!!!)
[2014-04-26 12:58:34] Stratum detected new block

Most probably it means you submitted several "shares", i.e. possible solutions, in that timeframe.

When you're mining for a pool, you don't solve blocks directly at the real coin's network difficulty but rather at a much lower one: the pool artificially lowers the difficulty before sending the packages to the miners so as to receive several distinct partial solutions.

Most of these solutions will be adequate only at the lower difficulty but others will be OK for a higher difficulty as well, among these hopefully one will be OK for the then-current difficulty of the network - the pool will take it and submit it to the network to earn the block's reward, such reward will then be partitioned proportionately among the miners depending on how many partial solutions ("shares") each submitted, thus their contribution to the final effort.

Even if you were mining alone, remember the target block generation times are meant to be an "average", in real life some blocks will be generated shortly one after the other or they may delay a lot, but in the long run the average is kept.

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