Christiaan,
Just to add a bit more to your explanation is that
The reheat decision speed on every take off was 100kts
If the little tag showed 4 then you needed 4 reheats at 100kts to continue
the take-off
If the little tag showed 3 then at 100 kts you could continue the take-off even if one reheat had failed
If above 100kts you could always continue with the take off, even if a reheat had failed [ always required 3 reheats working]
So if it was a "3 reheat day" and a reheat failed prior to 100kts then a further reheat failure between 100kts and V1 would require the take off to be rejected.
Hope that makes sense??