Not working if statements in Python

I have a problem with my if statements. It involves looking for a pair of strings and collecting the times and then subtracting them, but I don't get why it doesn't work, and with a small loop inside to count the difference and if it's less it prints it out:

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fh = open('Perfe.txt')
R=0
Z=0
for line in fh:
    line=line.rstrip()
    if not 'Service Permission' in line :
        continue
    Y=line.split()
    Time1=float(Y[1])

    elif not 'Assignment Finished' in line :
        continue
    U=line2.split()
    Time2=float(U[1])
    R=R+1
        if (Time2-Time1) <= 3:
            print 'time of Request setup end',Time2-Time1
        else:
            continue 
print R

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and the Data is

---

Time               
A1 139.637737000 Service Permission 

Time          
B1 141.167620000 Assignment Finished

Time               
A1 159.897737000 Service Permission

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