SetFieldValue - Formula

I am trying to set a field value using workflow by apply a complex formula using the Case When function. On the actions tab I have the following:

SetFieldValue
Trigger On: Before Reciord Submit
Event Type: create,edit
Condition: Product Classification = LED non-directional

Replacement (W)=case when {custitemtestlumens} <=136 then
ROUND({custitemtestlumens}/9.1,0)
when {custitemtestlumens} <=249 and >136 then
ROUND(({custitemtestlumens}+ 33.5)/11.3,0)
when {custitemtestlumens} <=470 and >249 then
ROUND(({custitemtestlumens}+ 118.5)/14.7,0)
when {custitemtestlumens} <=806 and >470 then
ROUND(({custitemtestlumens}+202)/16.8,0)
when {custitemtestlumens} <=1055 and >806 then
ROUND(({custitemtestlumens}+190)/16.6,0)
when {custitemtestlumens} <=2452 and >1055 then
ROUND(({custitemtestlumens}+340)/18.6,0)
when {custitemtestlumens} <=3452 and >2452 then
ROUND(({custitemtestlumens}+548)/20,0)