he studied the map a few minutes和 he studied the map for a f

1 a few more minutes在你的句子裏面是时间状语的一部分,完整的是for a few more minutes. 但这个for,在口语中经常被省略.
for + 一段时间---------表示某个动作的时间持续范围.
2 a few minutes -------解释为“几分钟”.
3 a few more minutes -------解释为“（先前看了几分钟,後来）又是几分钟”.