The radar map shows you exactly how ocean swells approach your chosen break:
TL;DR: Swell period is the number of seconds between one wave crest and the next passing the same spot. The bigger that number, the more powerful and organized the surf tends to be - a longer-period swell has been traveling longer, pulls water from deeper down, and hits the beach with a lot more punch than a short-period one of the same height.
This is exactly why the app doesn't just report a raw wave height and call it a day - the Energy (kJ) number on each hour bakes period into the calculation, and the quiver recommendation logic gives a longer-period swell extra credit over a shorter-period one of the same raw height. A 2ft swell at 16 seconds will generally outsurf a "bigger" 3ft swell at 7 seconds.
TL;DR: The swell height reported by a buoy or a model like the one this app uses describes the wave out in open water - it is not the same number as the face height of what actually breaks at your beach. Two spots getting hit by the exact same ocean swell can look completely different once it reaches the sand.
The gap comes down to exposure: how directly a given spot faces the direction the swell is coming from. A beach that faces straight into a NW swell will feel almost all of that swell's energy. A break tucked behind a point, only lightly exposed to that same NW swell, will feel a much smaller fraction of it - even though a buoy sitting offshore between them would report the identical raw height to both. This app scores every saved spot on exactly that kind of exposure, separately for northwest and south swell windows, which is why the same forecast can show very different numbers for two different beaches on the same day.
If the surf looks smaller than the raw swell number implies, exposure - not a measurement error - is almost always why.
TL;DR: The same swell can be glassy and perfect at dawn and mushy, blown-out slop by late morning - same waves, completely different wind.
Compare the red wind arrow to the yellow coastline shape on the map above: an arrow pointing from the yellow landmass out toward open water is offshore for that spot; an arrow pointing from open water in toward the landmass is onshore.
Tide changes how a swell interacts with the seafloor at a given spot, but there's no single "good" tide that applies everywhere - it's entirely spot-specific. A sandbar or reef break might need enough water to cover a shallow ledge and only really work on a rising or high tide, while a beach break with steep sand can turn fat and slow at high tide and only really come alive once the tide drops. The Tide reading on each hour is there so you can start noticing which tide stage lines up with your own best sessions at a spot over time.
Where available, each hour shows a side-by-side against Surfline's own forecast for the nearest spot Surfline has mapped, plus the difference between the two (this app − Surfline, so a positive height number means this app is calling it bigger).
A bit of spread between the two is completely normal and expected, not a sign something's broken:
Use it as a sanity check, not a tiebreaker - if the two agree, that's a good sign either is in the ballpark; if they disagree, the reasons above are usually why.
Recommendations are custom-tuned to your 9ft Longboard and 6.9ft Mid-length.