first block is counted as block 0, but when you like to measure something its kind of distracting always adding one.
While it makes sense when you compare it with a normal ruler which also starts at zero, zero in this case should be the start of the first block, reaching the end of it would be 1m already.
Hence its more intuitive that the abacus, as it measures directly the first block aka the first meter, that it shows 1 and not 0

should be as simple as just adding 1 to the distance in src\main\java\vazkii\quark\content\tools\module\AbacusModule.java onHUDRender method before converting it to a string

String distStr = distance < AbacusItem.MAX_COUNT ? Integer.toString(distance) : (AbacusItem.MAX_COUNT + "+");
mc.font.drawShadow(event.getPoseStack(), distStr, x + 17, y + 5, 0xFFFFFF);