It could be either, depending on whether they inserted the wrong letter initially, or reinforced just a small section of a blocked letter using a punch big enough to cover the defective area. You also have to consider the ability to sink a correction deep enough on the die if it had been hardened previously and the degree to which it had been softened in order to sink the new punch. The truth is, we don't know the circumstances and can only speculate.
There is however, strong circumstantial evidence on occasion to suggest insufficient depth of strike for the correction or change of date. The above may well be a case of this, but equally could be a repair to the upright of the B, as in this instance the use of E, F, I or L would all broadly follow the shape of the B.