Shiv,
I see a few things that are odd ...
1) The default max_transition for the library is 1.5. You applied a new max_transion of 1.2 but it didn't seem to take. Check that the syntax is correct.
2) Decimal places seem off in your report_constraint ...
1.500000 <- max_transition you are checking against
0.155956 <- transition of the cell being reported
slack---->0.1344044 <- how much this transition is passing/failing by
if 0.156 is your actualy transition time your slack should be 1.344 not .1344
as sameer said, do a report_delay_calculation. This will show your cell delay and output transitions, based on your input transition and output load. The .lib has this information also, but it is harder to figure out as it is a 2d array based on input transition and output load which the tool interpolates to get a single value.