can only be true means that the specified condition under Description is always true. For example, for the dead logic in the second row of the report, input1 < input2 is always true, which means that the condition, when evaluated, never evaluates to false. The reason that this is the case, is that the (input1 < input2) || (input1 == 0) condition is only evaluated when transition 1, input1 >= input2 is false (hence ~(input1 >= input2) is true), which guarantees that input1 < input2 will be true. For more information, see transition execution rules.
unreachable means that the specified condition never executes. In this case, the objectives involving substate A2 are all unreachable, because the transition (input1 < input2) || (input1 == 0) causes the state to be exited, and then re-entered. This resets the state, forcing the substate back to A1. Thus, the state A2 is never actually used by the chart.
