Hypothesis testing 1 poplulation mean

Hi im new here so

I am getting trouble with this question, here it is:

An advertisement for a certain model of mobled phones promised that it allowed '3.5 hours talk time'.A random sample of 8 phones of this type was tested of talk time, x hours, available were as follows:

3.4,3.7,3.1,3.2,3.6,3.5,3.3,3.4

{sum of x=27.2, sum of x sqrd = 92.76}

Carry out a test, at the 5% significance level, to examine whether the advertisement was overstating the length of talk time available from the phone.

"I got Ps= 3.4 so how do you get Q, i know that Q=1-P, but you will get a -ve!

Thanks