WSPR signal result when filters are used

What i found out today when i'm using my filters.

Normaly i will use 2.4khz , Roofng filer on Auto so wide ssb. This evening on 40mtr i turned down the filter to 600khz. The signal did inprove with more db's. Also i turned the Roofing filter on with the setting 3k. Is this normal what i see in the results? Ok we have fading but that much.. Look at RA9CUA 8db difference

Example

2010-01-24 22:54 W3GXT 7.040103 -11 0 FM19ol 5 PE2MC JO22ma 6154 48 (Setting 600khz roofing filter 3k)
2010-01-24 23:28 W3GXT 7.040103 -19 0 FM19ol 5 PE2MC JO22ma 6154 48 (Setting 2.4Khz roofing filter auto)

2010-01-24 23:28 RA9CUA 7.040041 -5 -2 MO07qc 5 PE2MC JO22ma 3569 285 (Setting 600khz roofing filter 3k)
2010-01-24 23:36 RA9CUA 7.040042 -13 -1 MO07qc 5 PE2MC JO22ma 3569 285 (Setting 2.4Khz roofing filter auto)

Can anyone explane this?

Marco