The number that left the camp on Saturday morning was 4*28 = <<4*28=112>>112 athletes
This means that in the camp there remained 300-112 = <<300-112=188>>188 athletes.
The new group trickling in on Sunday morning comprised 7*15 = <<7*15=105>>105 athletes
The number that slept at the camp on Sunday night is therefore 188 + 105 = <<188+105=293>>293 athletes
Since there were 300 athletes on Saturday night, the difference is 300 - 293 = <<300-293=7>>7 athletes.
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