Finite lifetime budgets become clearer when retained and lost counts are scanned. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The first row keeps four fifths

Prepared shots 100 split into retained 80 and lost 20. The retained fraction is 4/5.

80+20=100,fsurvive=4580+20=100,\quad f_{\text{survive}}=\frac{4}{5}
Survival scan rowRetained plus lost closes before the ratio.4/5retained1/5lostsurvival budget

The second row keeps seven tenths

The next budget keeps 84 of 120 prepared shots and loses 36. The exact fraction is 7/10.

84+36=120,fsurvive=71084+36=120,\quad f_{\text{survive}}=\frac{7}{10}
Survival scan rowThe bar fraction follows the same count ratio.7/10retained3/10lostsurvival budget

The third row makes the loss larger

The third budget retains 52 and loses 28 out of 80 prepared shots. The scan ends at 13/20 survival.

52+28=80,fsurvive=132052+28=80,\quad f_{\text{survive}}=\frac{13}{20}
Survival scan rowThree rows expose survival as a count ratio.13/20retained7/20lostsurvival budget