# Kotlin, 152152 119 bytes

{a:Int,b:Int->(a..b).map{String.format("%06d",it)}.filter{it[0].toInt()+it[1].toInt()+it[2].toInt()==it[3].toInt()+it[4].toInt()+it[5].toInt()}.count()}


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Taking two integers than convert it into six symbol strings and count.

Optimized it thanks to mazzy and his solution to 119 bytes.

{a:Int,b:Int->(a..b).count{val d="%06d".format(it);(d[0]-'0')+(d[1]-'0')+(d[2]-'0')==(d[3]-'0')+(d[4]-'0')+(d[5]-'0')}}


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# Kotlin, 152 bytes

{a:Int,b:Int->(a..b).map{String.format("%06d",it)}.filter{it[0].toInt()+it[1].toInt()+it[2].toInt()==it[3].toInt()+it[4].toInt()+it[5].toInt()}.count()}


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Taking two integers than convert it into six symbol strings and count.

# Kotlin, 152 119 bytes

{a:Int,b:Int->(a..b).map{String.format("%06d",it)}.filter{it[0].toInt()+it[1].toInt()+it[2].toInt()==it[3].toInt()+it[4].toInt()+it[5].toInt()}.count()}


Try it online!

Taking two integers than convert it into six symbol strings and count.

Optimized it thanks to mazzy and his solution to 119 bytes.

{a:Int,b:Int->(a..b).count{val d="%06d".format(it);(d[0]-'0')+(d[1]-'0')+(d[2]-'0')==(d[3]-'0')+(d[4]-'0')+(d[5]-'0')}}


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1

# Kotlin, 152 bytes

{a:Int,b:Int->(a..b).map{String.format("%06d",it)}.filter{it[0].toInt()+it[1].toInt()+it[2].toInt()==it[3].toInt()+it[4].toInt()+it[5].toInt()}.count()}


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Taking two integers than convert it into six symbol strings and count.