Experiences with rolled sheet chimney sealing?

Hello, I have commissioned a roofing company. The chimneys were leaking because the seals had rotted. Now the roofer has charged me for 10 m of rolled lead sheet (I would have expected a measurement in square meters). He wants 828.00 EUR for the 10 m. In addition, there are various other items. If I consider that the chimneys are approximately 50.0 cm * 50.0 cm and I have 3 of them, I wonder where he used 10 m of rolled lead sheet?! Can anyone help? Thank you very much

Oh, one more thing I forgot, the third chimney was only done halfway because the other half belongs to the neighbor.