underwater spawn given when attracted

land frog x 60
UW frog x 145
Froglet x 148
tadpole x 149

think I might have got it at last

Spawn comes every five frogs

When calculating the amount of sets
add ghostly frog total to UW frogs total

eg 103 frog plus 2 = 105
froglets 112
tadpoles 112

equals 105 sets and still 7 more adult frogs to come

Spotted
Land frogs 32
underwater frogs
ghostly frogs 5
froglets  79
tadpoles 80

Attracted no spawn)
Land frogs6 60
underwater frogs 103
ghostly frogs 2
froglets 112
tadpoles 112

you have attracted 103 frogs so far, 112 froglets & 113 tads. For ever tad & froglet you attract (UW) you get 1 UW frog. therefore you still have have 10 frogs or 2 more plates of spawn.

Spotted
Land frogs 32
underwater frogs 57
ghostly frogs 5
froglets  78
tadpoles 79

Attracted (gave spawn)
Land frogs6 60
underwater frogs 100
ghostly frogs 2
froglets 108
tadpoles 111

Spotted
Land frogs 29
underwater frogs 56
ghostly frogs 5
froglets  75
tadpoles 73

Attracted
Land frogs 55
underwater frogs 99
ghostly frogs 2
froglets 101
tadpoles 101

underwater spawn

Spotted
Land frogs 29
underwater frogs 56
ghostly frogs 5
froglets  73
tadpoles 73

Attracted
Land frogs 55
underwater frogs 95
ghostly frogs 2
froglets 100
tadpoles 101

The land frog is only useful for dropping spawn, either when you start frog breeding for the first time or if you aren't able to attract enough underwater frogs to drop spawn.  So although you don't need to spot any in other gardens to progress, people need them spotted in their own gardens.

The number of land frogs you spot in other gardens doesn't help with what you attract to your own - you get one land frog in your own garden for each complete set of tadpole, froglet and underwater frog you spot in other gardens.  The land frog doesn't count towards that.

Don't worry, I asked all these same questions way back when.  It's a very confusing challenge.

SPAWN ON PLATE

Spotted
Land frogs 28
underwater frogs 51
ghostly frogs 5
froglets 62
tadpoles 65

Attracted
Land frogs 55
underwater frogs 94
ghostly frogs 2
froglets 96
tadpoles 96