To add more context, I cleared the formula from the Yr10 column and was allowed to mirror the column. As the listed formulas below will show, other than a few variable changes all the formulas for the various yrs are the same formula, so why would a mirror error on what it has already allowed in the form of the previous Yrs formulas:
Yr 1 = initial number value
Yr 2 formula = IF(AND({Duration in Days}>365,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Value},(MULTIPLY(DIVIDE({AM Value},100),{RPI Yr2}))),2),IF(AND({Duration in Days}>365,{AM Type}="Fixed"),{AM Value}, ""))
Yr 3 formula = IF(AND({Duration in Days}>730,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr2 Value},(MULTIPLY(DIVIDE({AM Yr2 Value},100),{RPI Yr3}))),2),IF(AND({Duration in Days}>730,{AM Type}="Fixed"),{AM Value}, ""))
Yr 4 formula = IF(AND({Duration in Days}>1095,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr3 Value},(MULTIPLY(DIVIDE({AM Yr3 Value},100),{RPI Yr4}))),2),IF(AND({Duration in Days}>1095,{AM Type}="Fixed"),{AM Value}, ""))
Yr5 formula = IF(AND({Duration in Days}>1460,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr4 Value},(MULTIPLY(DIVIDE({AM Yr4 Value},100),{RPI Yr5}))),2),IF(AND({Duration in Days}>1460,{AM Type}="Fixed"),{AM Value}, ""))
Yr6 formula = IF(AND({Duration in Days}>1825,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr5 Value},(MULTIPLY(DIVIDE({AM Yr5 Value},100),{RPI Yr6}))),2),IF(AND({Duration in Days}>1825,{AM Type}="Fixed"),{AM Value}, ""))
Yr7 formula = IF(AND({Duration in Days}>2190,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr6 Value},(MULTIPLY(DIVIDE({AM Yr6 Value},100),{RPI Yr7}))),2),IF(AND({Duration in Days}>2190,{AM Type}="Fixed"),{AM Value}, ""))
Yr8 formula = IF(AND({Duration in Days}>2555,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr7 Value},(MULTIPLY(DIVIDE({AM Yr7 Value},100),{RPI Yr8}))),2),IF(AND({Duration in Days}>2555,{AM Type}="Fixed"),{AM Value}, ""))
Yr9 formula = IF(AND({Duration in Days}>2920,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr8 Value},(MULTIPLY(DIVIDE({AM Yr8 Value},100),{RPI Yr9}))),2),IF(AND({Duration in Days}>2920,{AM Type}="Fixed"),{AM Value}, ""))
Yr10 formula = IF(AND({Duration in Days}>3285,OR({AM Type}="Fixed RPI",{AM Type}="Variable RPI")),ROUND(SUM({AM Yr9 Value},(MULTIPLY(DIVIDE({AM Yr9 Value},100),{RPI Yr10}))),2),IF(AND({Duration in Days}>3285,{AM Type}="Fixed"),{AM Value}, ""))