Assessment tests are used extensively to measure student learning. Other than ability and prior preparation, student performance reflects their intrinsic motivation to do well on the test, affecting their effort on the test itself. We experimentally increase the numerosity (magnitude) of maximum points on the test to create an illusion of a more rewarding test and nudge students to exert higher effort on the test. Tested in three different settings, we find insignificant treatment effects in the high-stake test context (Setting 1) and low-stake test context (Setting 2) when an incorrect response does not attract a negative penalty. However, in a high-stake test context, when an incorrect response attracts a penalty (Setting 3), we find the likelihood of getting the question correct increases by 9.5 pp, with stronger effects on male (16 pp) and above-median ability (16 pp) students. We discuss increasing mental effort as the potential mechanism driving the effects.