Whatif Parameter issues

Using the whatif parameter feature to define a range of -1M to +1M in increments of 1000 with default of 0.

WhatIf BUDGET table

WhatIf BUDGET = GENERATESERIES(-1000000, 1000000,1000)

WhatIf BUDGET Value = SELECTEDVALUE('WhatIf BUDGET'[WhatIf BUDGET], 0)

However, the issues are:

input X = result Y

input 0 = -1000 (not ok)

Input 1000 = 1000 (ok)

Input 2000 = 1000 (not ok)

Input 3000 = 3000 (ok)

Input 4000 = 3000 (not ok)

Input 5000 = 5000 (ok)

etc

etc

I have tried changing the increment but same issue with slightly different results.

Setting start point of range to 0 solves this but not what we want.

Is there a known issue with the WhatIf Paramter using a negative to positive range?