Finding standard deviation difference t-test?

#1
Ok, I know the to find the mean difference, it's basically, the mean of C1 - C2. But how where did the 2.38 in the StdDev come from? It's surely not the StDev difference of C1 and C2, right? Similar with SE mean, I'm a bit confused. Thanks.

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Paired T-Test and Confidence Interval

Paired T for C1 - C2

N Mean StDev SE Mean
C1 4 5.75 2.63 1.31
C2 4 5.25 2.22 1.11
Difference 4 0.50 2.38 1.19

95% CI for mean difference: (-3.29, 4.29)
T-Test of mean difference = 0 (vs < 0): T-Value = 0.42 P-Value = 0.649
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8 6
2 4
6 3
7 8