[Xymon] [xymon]problems setting to 'derive'

[diffusion]

Hello,

I'm using 2 test using same data to compare the difference between 
gauge & derive (derive is the best choice, because data  that is 
continuously increasing in value between 00:00 and  23:59

When graph using Gauge, values are correct :
field03a: 5
field03b: 17
field03c: 14
field04a: 3
field04b: 12
field04c: 15
Total: 66

=> same values in graph

But when i switch to derive, values in graphs look like
field03a: 6m
field03b: 4m
field03c: 5.8m
field04a: 4m
field04b: 2m
field04c: 2m
Total: 0

Maybe i'm understing correctly 'derive' or there another things goes 
wrong ?

Graph Definition
[LogMsg]
         TITLE Nb 'Erreurs Sérieuses' par svi
         YAXIS Qtt
         -l 0
         DEF:field03a=LogMsg.rrd:field03a:AVERAGE
         DEF:field04a=LogMsg.rrd:field04a:AVERAGE
         DEF:field03b=LogMsg.rrd:field03b:AVERAGE
         DEF:field04b=LogMsg.rrd:field04b:AVERAGE
         DEF:field03c=LogMsg.rrd:field03c:AVERAGE
         DEF:field04c=LogMsg.rrd:field04c:AVERAGE
         DEF:Total=LogMsg.rrd:Total:AVERAGE
         LINE1:Total#1AEAEC:Total
         LINE2:field03a#18D859:svi03a
         LINE2:field04a#1D8A42:svi04a
         LINE2:field03b#D50038:svi03b
         LINE2:field04b#81112E:svi04b
         LINE2:field03c#182DD8:svi03c
         LINE2:field04c#171F63:svi04c\n
         GPRINT:Total:LAST: Stats de Total \: cur=%5.0lf
         GPRINT:Total:MIN: min=%5.0lf
         GPRINT:Total:MAX: max=%5.0lf
         GPRINT:Total:AVERAGE: moyenne=%5.0lf\n

Ncv def :
NCV_LogMsg="field03a:DERIVE,field03b:DERIVE,field03c:DERIVE,field04a:DERIVE,field04b:DERIVE,field04c:DERIVE,Total:DERIVE,*:NONE"


Someone have an idea ?