Change 308 to 307? There's no 308 in the formula.
if (cell) is less than (75), return (60)
if cell is greater than 75, but less than 101, return 80
if cell is greater than 101, return 100
By that description the formula doesn't return anything for 75 (or 101). I assumed

if cell < 75, return 60
if cell >= 75 and < 101, return 80
if cell >=101, return 100