Table:
text: 2008 United States motorcycle Grand Prix
MotoGP classification
MotoGP classification
Rider Manufacturer Laps Time_ Grid
Valentino Rossi Yamaha 32 44:04.311 2
Casey Stoner Ducati 32 +13.001 1
Chris Vermeulen Suzuki 32 +26.609 8
Andrea Dovizioso Honda 32 +34.901 9
Nicky Hayden Honda 32 +35.663 3
Randy de Puniet Honda 32 +37.668 6
Toni Elias Ducati 32 +41.629 10
Ben Spies Suzuki 32 +41.927 13
James Toseland Yamaha 32 +43.019 5
Shinya Nakano Honda 32 +44.391 12
Jamie Hacking Kawasaki 32 +46.258 17
Sylvain Guintoli Ducati 32 +55.273 14
Alex de Angelis Honda 32 +55.521 16
Colin Edwards Yamaha 32 +1:02.380 7
Loris Capirossi Suzuki 32 +1:08.207 11
Marco Melandri Ducati 32 +1:10.962 15

text: 2008 United States motorcycle Grand Prix
MotoGP classification
MotoGP classification
Rider Manufacturer Laps Time_ Grid
Anthony West Kawasaki 31 +1 Lap 18
Jorge Lorenzo Yamaha 0 Accident 4

Question: If the manufacturer is Yamaha and the laps completed were less than 32, what is the average of all grid sizes with these criteria for the 2008 United States Motorcycle Grand Prix?