One conditional formatting definition can be applied to multiple (discontiguous) ranges of cells and Excel will find the "Lowest Value" and "Highest Value" etc for the limits of the formatting.

However, it appears that if I have more than 253 separate ranges the conditional formatting breaks as Excel no longer finds the extrema of the ranges. Instead the "Lowest Value" and "Highest Value" the limits appear to be fixed to very small values around zero).

Is this a bug? A known limitation, in which case could someone point me to where it is documented? Are there any workarounds (aside from the obvious use fewer ranges / multiple formats / manually specify the limits)?

EDIT (This example is contrived and can obviously be implemented with a single range - my real use case has hundreds of discontiguous ranges spread throughout a worksheet).

Example: I have a 32x16 grid to which I have applied conditional formatting using the cell / range specification below, which contains 256 groups of 2 cells.

If I remove the first 3 entries ($A$1:$A$2,$B$1:$B$2,$C$1:$C$2), then the formatting is correctly applied to the remaining 253 groups of cells:

However, if I attempt to apply the same formatting with 254 of the groups I get:

If I manually set the endpoints then the formatting does work with 254+ ranges, it is only the calculation of the min and max values that appears to be failing.

Formatting groups (256 ranges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