I believe the answer is he was granted a pension two separate times by two separate acts of congress.
The act of 15 May 1828 made many soldiers who were previously ineligible (you had to prove need before 1828) suddenly eligible, so Arthur Bell applied for and received a pension under the act of 15 May 1828 along with many thousands of others. His pension under the act of 15 May 1828 began on 4 March 1831.
On 7 June 1832 Congress revised and extended the Rev War pension act, at which time Arthur Bell had to reapply and prove his eligibility. After proving his eligibility, he was placed on the new pension rolls created by the act of 7 June 1832.