if loops and Arrays

Im trying to plot some data from an experiment but the timer starts a bit before the start of my variable. I have tried to create a new list of times starting from 0 but when I do so my loop generates more values for my array then the length of the original array which makes it impossible to plot.

Aplate = np.loadtxt('Plates Angular poston_2.txt')

t1 = []
for i in Aplate:
    t = Aplate[:,0]
      for j in t:
      if j < 27.4150:
         x = j -3.01 
         t1.append(x)
     else:
         break 

y = Aplate[:,1]

plt.plot(t1, y)
plt.show()